Helps a lot and deals a lot of dmg

Energy runes for Zed is not bad idea..

Hrmm, let's see here.

1. To back up my statement of going more into the offensive tree, The way you're setting up your tree now isn't getting too much out of the Defensive Tree. By going into a 21/9/0 setup, you'd be gaining: 2% AS, 6 ArmPen, and 5% extra damage to targets below 50% health.

And you'd be losing out on: 10% reduced CC(doesn't add up to much more with Tenacity), 5% turret damage reduction, and a little bit of Armor and/or MR.

The 2% AS isn't much, but the ArmPen and extra damage alone should be worth going into the Offense tree. Percentage Armpen is applied before Flat ArmPen now, so that 6 flat ArmPen is worth quite a bit more. The damage increase is also really nice and works well with your passive. Chunk the enemy below half health before your Ult finishes, and it'll be doing 5% more damage.

As for the defense tree, you still get some of the best stats in here by going 21/9/0. 5% Reduced turret damage really isn't worth the point, considering you shouldn't be getting hit by the tower anyways. The tenacity is REALLY nice, but you're not getting its full effect with your current build, and the extra ArmPen and Damage outweigh its utility. If you really need to get out of CC, you'll be building Mercurial Scimitar/Mercury's Treads anyways.

Last off, going further into the Defensive tree really isn't a good idea. The extra health, melee damage reductions, and armor increases aren't really worth the points because you aren't a tank, and aren't going to be stacking stats that work well with these masteries. If you get focused, chances are these masteries are NOT going to save you. You're job as Zed is to kill as many of them before they can kill you. Because you're a glass cannon.

2. You forgot about the Passive and Lifesteal on BotRK. Those will give you plenty of health back, considering you want to melee your target at least once for your passive to go off, and the extra lifesteal works with Ravenous Hydra. Also, wouldn't the extra damage from BotRK active be worth it enough? It works with your Ult, so by using the active from BotRK, you'll be adding 175 damage onto your ult from this item, compared to the 85 that Gunblade would give you. That's not including the original damage the items themselves do, so...

BotRK: (Active)350+(Ult bonus)175=525 damage
Gunblade: (Active)170+(Ult bonus)85=255 damage

That's a whopping 270 extra damage from BotRK, not including its passive health shred(That applies to ult too!).

So that's some nice extra damage and life steal that I don't think is a good idea to ignore. If you're sticking with Gunblade though, at least make BotRK an alternate choice :)

3. Mercurial Scimitar is definitely a good alternative. Scimitar provides better flat out AD, MR, and a cleanse, while Maw provides more burst survivability through its shield, and increased AD at lower health percentages(it matches Scimitar's AD at only 87.5% HP, and goes up to a whopping 94 AD at 2.5% HP. Not always practical, but you're not often going to be at full health). Maw can also be used for baiting enemy APs into diving you.

First of all, thank you Sylnic to take the time to make a argumented comment .

1- It's the first time i ear Tough skin work only on jungle monster .
In all case i'm agree with you in fact i take tough skin and bladed armor because i have actually no idea of where spend this point .
My goals are :Durability, Veteran's scare, juggernaut , safeguard and tenacious (Stack with mercury boots)

So if you have a better idea of these 2 masteries i'll be glad to test this and change my guide .

3- Yes my goal is to build Zed as a assassin, but with my own experience , Offensive masteries are not a must have .
First of all is the amount of life you get (specially with doran's blade as a starter).
Secondly you get enough AD for your early but you are very squishy, Zed is an assassin but he need a minimum AD required for the assassination .
Before this state, you have to survive, and stack AD as soon as possible .
That's why i rush the BF .
On the mid/late game, masteries won't make a lot of difference with your full offensive items so that sound good for me .
nevertheless i can understand if many zed player try to be more aggressive than me, but it's not a safe way .
i'll make some test with new masteries

2- When i made my test for Zed items i took the blade of ruined king .
This item is very good .
a-Bonus movement speed for chase your target .
b-Drain passive : 150+50% of your AD so we are talking about something around 150+(400/2)=350 HP.
c-Extra damage of 350 .

Now compare this with Gunblade :
a- Active snare your target so it's pretty much the same idea .
b-Zed burst is something like 1500 dmg just with the mark explosion with 20 of Spellvamp .
(that can be more if one of your teamate have the ancient tome )
So we are talking about 300 of Health regen just with the mark, you can add the two others skills.
C-Extra damage around 170 (we don't tons of AP)

So basically you loose a little Damage (Not AD just damage, it's important to make the difference for the death mark explosion) but you get more sustain .

In some case take both can be really nice to survive to focus if you really don't want to take a defensive item .
I'll add some deviation on my guide later it's a good idea .

And Finally for the maw of malmotius :
I prefer mercurial scimitar : Anti CC , Movement speed , More resist magic, more AD than malmotius .
In early it's also better because you can rush the BF Sword and negatron cloak to make sure to win your mid lane .
You don't slow your AD Stacking road and get tons of Resist Magic .
Some other guide of Zed suggest this too .

A few critiques here. I know you said to test the build out before talking, but I'm gonna use game maths, logic, and what not to back up my critiques.

1. Tough Skin in the Defensive Tree is NOT the same as it was in season 2. The reduced damage only applies to jungle mobs in season 3, due to champions negating far too much minion damage in the early levels during season 2. The bladed armor effect does apply to lane mobs, but personally I don't see it being worth it.

2. ramuse123 had a good point of pointing out Gunblade, but he didn't really say why it was a bad choice. I saw you say that the spell vamp works great on Zed, but I think a Blade of the Ruined King is a much better choice if you're looking for pure damage output and sustain. With Gunblade you're spending extra gold on wasted AP, and the Spell Vamp isn't going to heal you as much as the active and lifesteal on BotRK unless you a. Can't melee minions/champions, or b. have a **** load of minions and champions standing on top of each other to be hit. In a team fight, gunblade just isn't optimal, and BotRK certainly gives a powerful passive with it as well.

3. If you're goal is to play Zed like an assassin, why put so many points into the defensive tree? I understand you have to survive to a point, but if you're going to be an assassin you have to have the damage of one, and Zed's mobility gives him enough survivability if you maneuver him right. Going 21/9/0 will give you plenty of damage while helping you stay alive during early-mid game. If you need more survivability, that Frozen Mallet will give you plenty of health.

4. I'd suggest giving some options for deviation, because you always have to build certain items based off the enemy team's success/comp. For example, I would throw Black Cleaver as an alternative to Last Whisper. It gives you bonus health, damage, CDR, and arm pen for your team that stacks. Against a team that's not stacking armor, Black Cleaver is a much better item choice. If you grab BotRK instead of Gunblade, this will give you enough gold to pick up a cleaver instead of a Last Whisper

5. Maw of Malmortius is never a bad idea, especially if you're laning against an AP champ. Pick up that Hexdrinker early and you'll be able to survive that crazy burst other mids put out.

That's about all I can think of or care to type out at the moment. Have fun!

:(

Yes Gunblade .
Make your own test before downvote .

When i find how to transfert a LoL recorder as a normal video i'll post here for show this .
the spellvamp is very amaizing on a Zed .

gunblade?!? -.-

Thanks mate, i'm glad to have some feed back :)

For an incomplete guide, it looks pretty complete :P

It is a bit plain, but a little work here and there and it should look fine.

Well done