Zac top or mid
Threats to Zac with this build
|Alistar||This lane is a joke. Once you hit level 2, look for any opportunity to trade. His abilities cost a ton of mana and do little damage. The only danger you have is if the jungler shows up, so try not to push the wave and ward up. Once you have Spirit Visage, he can't trade at all unless he is building like a bruiser and even then you should win almost all trades. (https://www.youtube.com/watch?v=AB8CtE4u7eI)|
|Blitzcrank||Looking forward to the day I fight a solo lane Blitzcrank. I can't imagine Blitz would do well. Will update this when it happens.|
|Braum||Another incredibly easy lane. Very low damage without items. His shield also does not block any of your abilities. Only danger is the jungler, so ward up.|
|Leona||This lane is a joke. Build magic resistance and ward up. She can't kill you without a jungler.|
|Malphite||One of my favorite lanes. Once you hit level 2, look for any opportunity to trade and poke. He will run out of mana long before you die. Your Stretching Strike has a shorter cooldown then his passive shield so look to constantly harass him so he doesn't get his shield. Make him choose between getting farm and having a shield. Sooner or later, you will force him back or all in and kill him.|
|Rammus||This lane is a joke. Trade whenever you can. Your only fear is the enemy jungler so ward up and have fun!|
|Taric||I look forward to the day I fight taric top. Will update when it happens.|
I have been playing league since its release and for years the best I was able to do was get to silver 1. Then I discovered zac. At first I took him to the jungle with little success. However, at the end of season 3 (after zac was nerfed), I took him to mid and top lane and climbed to diamond. I am currently ranked #2 solo lane zac in NA on OP GG (zacs with less then 100 average cs are junglers). Hopefully, through this guide, you can learn to bounce your way to the top. Also check out my Youtube Channel for more videos and my Zac Stream where I am always happy to answer questions. This is still a work in progress, but I won't be satisfied until I have covered every lane matchup and every nuance of playing Zac, as well as have a video example for everything.
Lately I have been having success running two different rune setups. One I use against predominantly physical damage teams (30% CDR at level 18) and one against predominantly magic damage teams (20% CDR at level 18). I swap out magic resist for CDR depending on my needs as I no longer like Abyssal Scepter and would prefer not to buy it unless the enemy team has a lot of magic damage.
Magic pen marks: Since zac has very high base values on his damage, magic pen provides a substantial increase to his damage output. In teamfights, this extra magic pen can be the reason why you one shot an enemy carry.
Flat armor seals: In general, I prioritize armor over health as I feel it makes your opponents commit to fights they cannot win by thinking they can kill you because your health is low. I chose flat armor seals over armor per level seals because you generally end the game with 3 armor items and can really use that extra armor in the laning phase.
Scaling magic resist runes: Since you only tend to build one magic resistance (mr) item (spirit visage), any additional mr you can have at the end game is nice. Another good option is flat cdr or cdr per level as it both increases zac’s damage by allowing you to cast more abilities and provides more sustain from the extra blobs generated. If you are fighting a team that is only physical damage however, you could get cdr per level runes instead of magic resist per level runes.
Scaling cooldown reduction runes : I run 3 Scaling cooldown reduction runes to get a total of 20% (with the quintessences) CDR on Zac by level 18. With the masteries and two CDR items, you will hit 45% by level 18. Cool down reduction (cdr) gives both more damage and sustain. CDR is amazing on Zac especially in the late game as it will allow you to use elastic slingshot multiple times over a fight and have your ult ready for any teamfight.
Cool down per level Quintessences:
UPDATE: Added info on courage of the collossus, green fathers gift, and fearless
I tried a few different keystones and here are my thoughts:
Deathfire Touch is just too weak since you only get Liandry's Torment. This means you barely take advantage of the ap and ad ratios. Thunderlord’s decree’s base damage is high enough to be worth using.
Grasp of the Undying is a solid choice. The main reason why I don’t use it is playstyle. In general, as zac, I don’t like auto attacking the enemy champion as it will get enemy minion aggro. Sometimes the difference between winning a trade and not is minion damage so I would rather let my lane opponent take the extra minion damage while I just use my abilities and pick up my blobs.
Courage of the Colossus is an amazing keytstone on Zac as it provides a huge shield in teamfights and make you basically unkillable until your ultimate is over. It is much less useful in the laning phase though as the shield is pretty small if there is only one enemy champion nearby and its cooldown is long. In the end, I think it is the best keystone for Zac, but I won't use it as it does not suit my playstyle as I like to be aggressive in the laning phase and like to carry teamfights through damage.
Thunderlord's Decree adds noticeable damage and works well with the e q w combo. Being able to use it every 20 seconds for a considerable boost in burst is amazing in the laning phase. I frequently get many kills because of the extra burst it adds to my all ins coupled with ignite. Nobody expects Zac to be able to do 500+ damage of burst at level 5.
Other masteries of note:
Runic Armor gives 8% more healing which is huge for zac. His passive heals zac for 4% of his max health and towards the end of the game, the 8% from runic armor could mean a few hundred health over the course of an extended fight.
Intelligence is nice since cool down reduction (cdr) both increases zac’s damage by allowing to cast more abilities and provides more sustain from the extra blobs generated. Since there is only one item I generally get that provides cdr (spirit visage), any additional cdr you can find is huge
Greenfather's Gift looks nice for top lane Zac, but I hardly ever used it and never noticed the damage it added. It could be good, but it would require a dramatic shift in playstyle for very marginal returns I feel.
Fearless adds noticeable armor and magic resist for teamfighting. I am still testing it out, but I think I will use fearless over perseverance and insight for now.
UPDATE: Just wanted to put some thoughts down before I make a serious edit to this section. Abyssal Scepter is no longer a must buy item on Zac. Magic penetration made the item great for killing squishy back line targets. I still like the item on Zac, but I feel like Liandry's Torment has once again become the must buy damage item on Zac again. I still buy fiendish codex early to max out my CDR, but I almost always complete Liandry's Torment before finishing Abyssal Scepter. Also, if there is no one on my team that does magic damage, I just skip Abyssal Scepter all together.
Also, the recent changes to Banner of Command make it an item I can't buy on Zac anymore because of the wasted mana stat.
For starting items, I either start Cloth Armor and 4 healing potions (against a physical damage champion) or Doran's Shield and a potion (against a magic damage champion). The reason why I start Doran's Shield is because it gives health (which helps your passive), passive healing and auto attack damage reduction. I don’t like Doran's Shield, but I can’t think of a better starting choice against magic damage champions.
In general, I always start off by completing a tanky item and then following it up with Abyssal Scepter. The tanky item depends on your lane opponent. If you are fighting an auto attack heavy physical damage champion like Aatrox, Tryndamere, or Yasuo, I like to build Thornmail first. If you are fighting a spell based physical damage champion like Wukong, Garen, or Gangplank, I like to build Sunfire Cape first. If you are fighting a magic damage champion, rush Spirit Visage. If you are playing against a champion with lots of hybrid damage like Jax, bruiser Fizz, or bruiser Nidalee, rush Abyssal Scepter and Thornmail. Against jax, you may want to buy Thornmail first.
Detailed item analysis:
Thornmail: This item is my personal favorite item to get on zac. It allows you to duel physical damage champions with confidence. In the end, zac’s passive means your health pool is actually larger than your opponent will anticipate as you will be picking up blobs while fighting. I cannot tell you how many times a tryndamere will go all in and find himself burning his ult while I am still at half health (add video link). Thornmail is also the item that allows you to dive the enemy ad carry with confidence knowing that they will kill themselves long before they kill you (add video link).
Abyssal Scepter: When Abyssal Scepter had magic penetration and CDR, it was a must buy. Since they removed the magic penetration, I only buy it if I am up against a mostly magic damage team.
Spirit Visage: This item gives you all the healing and resistance to magic you need. The increased healing on your blobs can allow you to survive fights that would kill lesser champions. Once you have this item, you can fight most mid mages and win. Must buy unless they run all attack damage composition.
Liandry's Torment: This item will provide all the damage you need to one shot squishy back line champions. If you land Elastic Slingshot (e), into Let's Bounce! (r), followed with Unstable Matter (w) and eventually Stretching Strike (q), most backline champions will be either dead or nearly dead. If you land Elastic Slingshot onto 3 or more enemy champions, you may win the fight by default since you will do so much damage. Even though this is the only damage item I buy on zac, it is very common for me to have the most damage dealt to champions by the end of the game.
Sunfire Cape: Provides armor, health and a point blank burn aura. I generally buy this as my fifth item to add more durability and damage.
Randuin's Omen: If the game goes long enough, Randuin's Omen provides considerable tanking stats to help you survive end game ad carry damage. In the end, it's almost always the ad carry that hits hardest over time, so having that passive crit damage reduction will add up over a long fight.
Banshee's Veil: In most cases you will want Spirit Visage and Abyssal Scepter as your only magic resist items. There are two instances where you will want to rush Banshee's Veil instead. If the enemy team has a Janna or a Poppy, you will want Banshee's Veil. Your main engaging tool Elastic Slingshot is easily canceled by either of those champions and you will find yourself in a VERY bad place.
Banner of Command: This item is no longer purchasable on Zac as it is just too inefficient stats wise.
Zz'Rot Portal: Another item I have begun to appreciate only recently. I will either buy it as my second item on games I can rush Banner of Command (to compound Banner's power) or as my 4th/5th item to help split push/siege. See "More information on Banner and Zz'rot" below for a more in depth explanation of the benefits of this item.
Rylai's Crystal Scepter: I almost never buy Rylai’s on Zac because zac already has a 40% slow in his Stretching Strike and two knock ups in his kit and a low cooldown (when fully ranked) gap closer. He doesn’t need the slow and Liandry's Torment provides all the damage you ever need.
Warmog's Armor: Another great item I almost never get. The main reason for this is that I like to have tankiness in armor and magic resist so people will over commit to kill me when they see I have low life (it happens all the time, even in diamond)(FIND CLIP). Another reason why I avoid it is because Zac doesn’t need the passive healing it provides because of all the healing already in his kit, especially by the time Zac gets 3k life. If you choose to run 10% CDR Runes, Warmog's is a useful buy to get you maxed out.
Ninja Tabi: I don't buy boots anymore unless I am in the jungle, see Jealous of Cassiopia at the bottom of the items section.
Mercury's Treads: I don't buy boots anymore unless I am in the jungle, see Jealous of Cassiopia at the bottom of the items section.
Sorcerer's Shoes: Magic penetration is a great stat on Zac. When I jungle as Zac, I pick up Sorcerer's Shoes all the time for that little extra burst while ganking. In lane though, I don't buy boots anymore, see Jealous of Cassiopia at the bottom of the items section.
Zhonya's Hourglass: Another great buy in theory. The cooldown reduction, damage, and armor are all nice. Maybe purchase first or second when fighting a Zed? Not sure. Great if you go full AP Zac (which I now do vs Trundle to counter his ultimate). I don't buy it unless I plan on going heavy AP.
Hextech Protobelt-01: I like this item, but I just don't prioritize it higher then other available CDR items. It gives health, ap, and cooldown reduction. It also gives a short ranged blink that does decent area damage. The only problem with this item is that you can't use it mid ultimate like you can with flash. It is still great for re-positioning yourself after missing an elastic slingshot or catching up to an enemy when your elastic slingshot is on cooldown. I don't tend to buy it much though unless I really don't need Spirit Visage.
Void Staff: Now that I buy so much magic penetration I find Void Staff to be a really nice supplement to my damage in the late game. I sometimes buy it as my 5th or 6th item now.
Jealous of Cassiopeia: So, um, I don't buy boots on Zac anymore. In the 6.9 patch, they gave Zac 5 extra movement speed. It got me to thinking that boots really don't help Zac when it comes to fighting. Normally you want boots to catch up or run away from the enemy, but you are Zac, with 45% CDR, so you can use elastic slingshot to catch up or run away from the enemy (7 second cooldown is insane). When you land elastic slingshot, you can ult, which gives you 20-50% movement speed. So I stopped buying boots. I know it sounds strange, but I have been climbing steadily since this patch. I have been running no boots for a few months now and I really like it. Could still be useful if you have a rough lane (Illaoi or Darius for example) to dodge their skills shots and run away during the laning phase.
The only viable summoner spells for Zac are Flash, Ignite, or Teleport. In almost all cases, I take Flash and Ignite when I go mid or top zac.
Flash: The generic uses of being able to Flash to escape death or chase down an enemy is great all on its own. Add to that the ability to Flash behind an enemy and use your ultimate to knock them toward waiting teammates and you see why Flash is a summoner of choice (Flash ultimate on Irelia). You will not always be able to Elastic Slingshot into the back line, so Flash gives another opportunity to place yourself where you want in the middle of the enemy team (INSERT VIDEO).
Another great use for Flash is to use it mid ultimate to surprise and knockback one more enemy. Let's say you Elastic Slingshot into the enemy back line landing right behind an enemy Brand but missing the enemy Ezreal because he arcane shifted away. You use your ultimate to knock Brand towards your team and start chasing Ezreal. Right before the second or third bounce lands, you Flash behind Ezreal so the bounce knocks him towards your team. He will have no chance to react as you flash right before the bounce lands (FIND VIDEO).
Ignite: I prize Ignite for two main reasons. In the lane, it provides that little bit of extra burst that will allow you the confidence to get a kill. I can’t tell you how many times an enemy will stay at a quarter of their health only to die to a point blank Elastic Slingshot (e), Stretching Strike (q), Unstable Matter (w), Ignite combo (INSERT WINGS VIDEO). The second reason is that it will allow you to secure a kill on the enemy ad carry during teamfights. When you have Thornmail and Liandry's Torment, you are almost guaranteed to kill an enemy ad carry if you land your Elastic Slingshot on them in a teamfight thanks to Ignite. Your Elastic Slingshot, followed by Let's Bounce!, and Unstable Matter should instantly take the enemy ad carry to 20-30% health. The second bounce and Ignite should be enough to finish them off, especially if they try to auto attack you and take damage from Thornmail. My favorite example of this was in a game against Doublelift. I was at half health with Liandry's Torment and Thornmail. I had 100 less cs and was lower level. Even then, when I landed my elastic slingshot on his ashe, I took him from 100-0 without help and without him being able to fight back. Check it out here.
Teleport: Teleport is another viable summoner for Zac though I almost never take it because I feel like the three great strengths of Teleport don’t work well for Zac.
1) Teleport allows you to return to the lane when the enemy gets you low so you don’t loss any farm or risk your life by staying. However, since you are playing zac, the passive ability to revive and the incredible healing of your passive allows you to stay when most other champions would have to back. That, and the ability for Zac to last hit well under the tower means you can just wait for the wave to hit your tower when you are low so you can heal and continue to farm. Staying can also give you a level lead which opens up new opportunities for kills (INSERT VIDEO).
2) Teleport allows you to gank the bottom lane and help secure a kill or two during the laning phase. However, since you are playing zac, you rely heavily on the element of surprise for your kills. It is incredibly easy to dodge elastic slingshot if you can see it coming (INSERT VIDEO).
3) Teleport allows you to split push and still join your team when they need you. However, since you are playing zac, you do very little damage to towers. Sure, you can wave clear really well, but it takes forever to kill a tower as zac. That, and like it was mentioned above, you tend to work best with the element of surprise.
That said, if you are playing as a 5 man premade, always take Teleport so you can be a team player!
Cell Division (passive): Zac’s passive has two important qualities. First, each your abilities cost 4% of our current health and produce a blob if you hit an enemy champion that will heal you for 4% of your maximum health. This means that if you pick up every blob you will gain more health then you lose. If you have Spirit Visage, it heals for even more. For more information see Blob Management under the chapter Zac Specific Mechanics. Second, if you are ever reduced to 0 health, you will split into 4 parts and revive if any make it back to the center. This passive has gotten me so many kills, since certain champions can’t kill zac passive alone and mana reliant champions with no mana usually can’t kill it in time (INSERT VIDEO). Also, when you revive, you always revive with at least 10% of your health, no matter how low your blobs get. When you do revive in these cases, you can sometimes get a kill by instantly using Elastic Slingshot, followed by Stretching Strike and Unstable Matter. The following videos showcases both elements of Zac's passive (Team fight blobs, Extended Duel).
Stretching Strike (q): Stretching Strike is your bread and butter ability for the laning phase. It allows you to harass the enemy champion and last hit minions that would otherwise be unreachable. The base damage of Stretching Strike is high, so if the enemy champion does not build magic resist, they will take noticeable damage from the ability. The slow also sets up an easy to land Elastic Slingshot for an even better trade or all in (insert video). It is also a great disengage tool and can be used to bait out enemy abilities (insert video).
Most champions in the game have an auto attack range that is the same range as stretching strike or shorter (including Teemo). If Teemo was trying to harass zac, you would try to use it right as he is auto attacking you. If you hit him, you will do roughly the same damage (or more) but will win the trade because you can now walk away since he is slowed and your allied minions will attack him. If you pick up the blob, you will win the trade in a massive way.
Unstable Matter (w): Although unstable matters damage at early levels is low, it has the shortest cooldown of all your abilities that gets shorter as you pick up blobs. The short cool down means you can get a lot of extra healing by spamming your abilities, and using Unstable Matter as you pick up blobs. Also, since Unstable Matter does % max health damage, in the late game it becomes quite potent, especially against tanks. Since you also get Liandry's Torment, it means you have two sources of % health damage built into your kit.
Elastic Slingshot (e): Games are won and lost by how you use Elastic Slingshot. It has the longest range of any basic ability in the game (when max rank 1800), very high base damage, and a slight knockback that disables enemies for 1 second. It also generates a shadow at the location you land in and can easily be dodged if enemies are paying attention. I noticed that before Plat 1, almost no one ever notices the shadow.
In the laning phase, Elastic Slingshot has 3 main purposes:
1) Escape: If your lane is pushing towards the enemy tower, Elastic Slingshot can be the only thing that helps you survive a gank. Don’t use it except to get a kill (INSERT VIDEO) or to run away (INSERT VIDEO) if you are pushed in, otherwise, bad things will happen (INSERT VIDEO). Also, pay attention to what hard crowd control (snares, stuns, silences) the enemy team has. Wait for them to use them before you start Elastic Slingshot (INSERT VIDEO), otherwise, bad things will happen (INSERT VIDEO). Try to angle Elastic Slingshot so you have two different places you can jump to to escape and choose the path farther from the enemies.
2) Harassing: If the lane is pushing towards your tower, you can use Elastic Slingshot to harass the enemy laner, knowing that you probably won’t need it to escape a gank. If flash, Let's Bounce! and your passive are on cooldown, you may want to forgo using Elastic Slingshot to harass just in case. The two ways you can use it to harass are to use it at point blank range (so it can’t be dodged) (INSERT VIDEO), or after landing a Stretching Strike (so it is hard to dodge) (INSERT VIDEO). After landing Stretching Strike, use Unstable Matter before walking away and picking up blobs if you can.
3) All in: When you see your opponent is getting low on health or your jungler is on his way, you may want to use Elastic Slingshot to go all in. The three best ways you can do this is by using it at point blank range (so it can’t be dodged), after landing Stretching Strike (so it is hard to dodge), or by hiding in the brush or behind a wall (so they don’t see you charge up elastic slingshot) (INSERT VIDEO). If you have your ultimate ready, aim right behind the enemy champion, so the knock back from Let's Bounce! will knock them away from escape.
In the teamfight phase, Elastic Slingshot is how you get to the enemy backline. If your team really needs it, Elastic Slingshot can be used to peel for your backline, however, I almost never do this because Zac can single handedly take the backline out of a teamfight and scatter the enemy carries. Before the teamfight, it is important to identify priority targets and how likely you are to hit/kill them. I first prioritize squishy carries that are often found in the mid lane or the enemy ad carry. Then I look at my odds of landing on them. An enemy ashe or brand is a high priority target since they have no mobility and no escapes and it is easy to land Elastic Slingshot on. An enemy ezreal or fizz is a low priority target because their mobility means that if they are paying attention, you will never land your elastic slingshot on them. Priorities can shift though if a hard to hit carry uses their mobility. If vayne just tumbled, she becomes a VERY high priority target as you may be able to lock her down and kill her before she can tumble or condemn you. If you hit 3 or more champions, you may win the teamfight right there with the follow up damage from Let's Bounce!, Unstable Matter, and Stretching Strike (three man Elastic Slingshot). Also, try to aim right behind your targets so Let's Bounce! will knock them towards your team . If there are no priority targets that you can jump on with confidence, it may be best to just peel for your back line or go in when the enemy team engages and the priority targets may not be paying attention to you.
One last thing to mention, knockups and knockbacks can cancel elastic slingshot (Even Riven Knockup). That makes champions like Janna and nami very annoying. You may want to just wait until they have used their abilities or when they are preoccupied to jump in.
Let's Bounce! (r): Three things to note about Let's Bounce!.
1) You can’t use Stretching Strike or Elastic Slingshot while it is active. You can still use Unstable Matter while you are bouncing so spam that and pick up blobs if possible.
2) It increases your movement speed the longer it is active making it a great escape and chasing tool.
3) It has a long lasting knockback (1 second) that pushes targets a noticeable distance away from zac. The knockback can be used to push enemies towards your team or into tower range (INSERT VIDEO). Another fun use is to knock enemy minions away from your tower exposing enemy champions to turret fire (INSERT VIDEO)
Zhonya's Hourglass and bard ultimate will prevent future bounces from doing damage until after the effect wears off on Zac (INSERT VIDEO). It is also possible to die before Let's Bounce! does any damage… (INSERT VIDEO)
Zac Specific Mechanics
Controlling the minion wave: Zac is a champion that is an expert at fighting under allied towers. His abilities are on short cooldowns and have high base values allowing you to last hit most minions that make it to your tower. In addition, if enemies try to fight you under your tower, you have your passive, Cell Division, to fall back on in case they do enough damage to take you down. Something not all players know is that attacking one of your four blobs when your passive is popped will draw aggro from towers. I have gotten many kills because of this (INSERT VIDEO).
The reason why I mention that zac is an expert at fighting under the tower is that in general, you always want the lane minions pushing towards your tower. It means you are less likely to get ganked by the enemy jungler while also encouraging your own jungler to come gank. With all the crowd control (cc) that zac brings, it is really easy to get a kill when your jungler comes to gank so you want to encourage them to come. At the same time, it is really easy to push the lane as zac since each and every one of your abilities has an area of effect and can hit multiple enemy minions. If you are pushing the lane as zac, it also means you should not use Elastic Slingshot to trade or harass in case the enemy jungler does come which limits your options when trading. One of the first things you must do to master zac is get an understanding about the size of your Stretching Strike and your Unstable Matter. If you can position yourself to get last hits by hitting only the minions you want to kill, you will minimize the chance that you will accidentally push the wave (insert video here) and generate a blob to heal yourself with at the same time. If you can hit the enemy champion at the same time, even better (insert video).
Last hitting under tower: One problem with Zac is that all of his abilities are AOE. Before you can really last hit well under tower, you need to understand the size of the AOE of each of his abilities to the point where you can be precise about which minions you hit. As for the minions themselves, let me give some tips about them. For melee minions, a full health minion will die to an auto attack after two tower shots. Eventually, it may take an auto attack and an Unstable Matter, but that is easy enough to adjust to at that point. It really helps to know how much health a melee minion should be at after each tower shot so you can adjust and get the last hit even if they take damage before hand. In those cases, you may need to use Stretching Strike to last hit or to get it low enough to kill it with an auto attack. Being precise is important or you may hit other minions with Stretching Strike and lose those last hits. For Ranged minions, they will die to one auto attack and one Unstable Matter after taking a tower shot at full health. If all three ranged minions are full health and nothing is attacking them, you can hit all three with Unstable Matter to simplify last hitting. Eventually, it will take an extra auto attack to kill them, but that is after 10 minutes or so. If they take damage before the tower shot, it is hard to get the last hit, but its still possible if you use Stretching Strike (and maybe Elastic Slingshot) in addition to auto attacking and using Unstable Matter. To be honest, this is something that takes a lot of practice, but it is key to succeeding on Zac, especially against lane bullies like Renekton and Darius who like pushing the wave under tower.
Blob management: Sometimes picking up a blob can be a mistake your enemy laner can capitalize on. It means you either need approach blobs indirectly or not pick them up at all sometimes. At the same time, enemies can sometimes try to stamp out your blobs too zealously, missing opportunities to harass you and missing farm. When they go to stamp out your blobs, you can use your Stretching Strike to harass them and make more blobs. Also keep in mind that your blobs reduce the cooldown on your Unstable Matter that can be used to trade or farm.
Baron steal: Even without smite, zac is one of the best champions to use in order to get a baron steal. As long as you are in the fog of war, and they don’t know you are coming, it is worth the risk. When Baron gets to around 3k health, start charging Elastic Slingshot. When baron gets to around 2k health fly into the pit, aiming for a spot that hits both the jungler and baron (and as many other people as possible). When you land, immediately use Let's Bounce! and Unstable Matter. If you are lucky, the burst from your abilities will kill the baron before the jungler recovers from all the knockups and can smite (Smiteless Baron Steal). The baron pit also makes an excellent place to teamfight (2 v 5 in the Baron pit). One more Baron steal for fun.
Zac is primarily a team fighter. What I mean, is that Zac wins games by being with his team when they need him unlike a champion like Tryndamere who tends to win the game by split pushing. This means that when the laning phase ends, you should spend most of your time grouping with your team and looking for opportunities to fly into the enemy back line or looking to make picks. I consider the laning phase over when your tower or your opponent's tower is destroyed. When either of those things happen, that is when I usually start to roam. If I can though, I push the wave before roaming, but you need to use your best judgement here. If people are gathering or allied lanes are getting pushed in, you may want to just head right to your allies and forgo pushing the lane first. At this point, you want to look for points where you can hide in the fog of war and Elastic Slingshot vulnerable targets. Great places to hide are here (INSERT MAP). Usually, you want to aim right behind your target so that your e will just barely hit them. However, for targets with slow moving mobility (like tristana or aatrox), you may want to aim a little farther behind them just incase they notice the shadow that e makes and start their jump before you land. If you aim it right, you will interrupt the escape ability and almost always secure the kill at that point (INSERT VIDEO).
1.1 - Added info for Banner of Command and Zz'rot portal to the Items section. Added info for last hitting under tower to Zac Specific Mechanics. Updated item sets to include Banner of Command and Zz'rot portal. Changed the format a bit to make it easier to find sub-sections.
1.2 - Added preliminary assessment of item changes in 6.9 under the Item section
1.3 - Updated all item choices to my current bootless build and updated my rune page sections.
1.4 - Updated a lot of the matchups.