This guide is not a detailed or a great guide...
But this items, runes and masteries are in my opinion the best on Zac.
So if you need a short guide with items, runes and masteries, this is the best! ;)

With this build you have nearly 6000 hp on Zac and do also insane damage in Teamfights, with 40% cdr, nearly 30-45 magicpen and a max-hp based aoe ability every 1-2 sec.!

See runes.

Zac only need cdr in the offense tree and of course D.E.Sword is op ;). Rest Tank monster masteries.

The new accient Golem is superior on Zac, so go for it.

The new passive gives you 25% extra health on every bonus health, so we try to stack it.

We also want to have a high damage output. This is very easy on zac. Just stack magicpen (See runes). Also we go sorc. shoes for magicpen. With only sorc. shoes you ignore now nearly 30 magicresi. So most champs wont have much magicresi left!!
If you are early ahead, maybe with 2 or 3 good ganks, go for haunting guise. Now you have nearly 45 magicpen!!!

The next 2 items are the best tank items on zac atm. Nothing to say at.

We now go for warmogs cause it gives us 1280 hp instead of 1000. Now better then GA.

The last item is absolute situational. So choose what you need: More armor, more magicresi or more damage.

To discuss:

rylai's, sunfire, guardian angel, abyssal szepter

First of all rylai's:
Yes it gives hp and ap. Hp is good on zac, but you don't really need ap on zac. The passive is great and synergize with liandrys, but most of your spells have already cc, so wasted. Don't go for it!!!

Guardian angel:
Is a great item even on zac. But we try to stack hp, so warmogs is better atm. And most of the time you don't want to have it as the last item, cause other items are in that situation better. For example: you are against an auto-hit based team (like irelia, master yi, yasuo, cait and nunu) thornmail is op ;)
So i can't think of an situation you want to go for ga over other items.

sunfire and abyssal:
Great combo, but you want to be more tanky. If you are realy ahead and you need to carry...(Yes happend sometimes) go for it, but if you fail you aren't that tanky then. (With that combo + haunting you melt enemies, if you are ahead ;) you do in the early to mid game more than true damage to squishy champs)
So don't go for it except you have to carry! - Really if you have other good damage sources in your team, you are as a 'full' tank much stronger and you do even that way enough damage.

Thx for reading ;)

Standard

Standard jungle spells on Zac.

New meta allows now tank-jungler. Zac is one of the best. You need practice on him, like on every champ. He gives very much cc. In my opinion stronger than ammumu and hard underrated.

Pros

• Very much CC
• Lategame somewhat unkillable
• High burst (over 1000 damage at least)
• High damage over time: every 1-2 sec 6% of max-hp
• High mobility
• Great long-range ganks

Cons

• weak early game
• skins

... You know how to jungle. If not read how to jungle...

You are the main Tank and the initiator. Zac is perfekt for it. Your Goal is to soak up most damage and interrupt the enemy team.

Don't forget you can smite while slingshot. And you can use your w during r, so get all your bubbles when you are r in the enemy team and spam your w every sec or faster ;).

Combo: e in to enemy instant q + w then r and as much and fast w as possible -> enemy team dead or you was just on your own...

Help your Team!! Buy wards and gank! Farming is secondary.