First of all, he's tank. Second of all he is good early as a jungler as he Es from invisible spot (wards are less early game) and then scales to be a monster late game Going off of that point, he can e into the adc and then dominate the team fight initiation...
God...
Zac was the best jungler in the game, before he got nerfed to the ground. You can counter jungle him and kill him, because he goes low when he spams abilities to clear camps. Morello, Ignite, Smite, AOE dmg, Silences, CC, dashes, dispacement effects - Lee, Xin, Tristana, Janna, Gragas. Champions with knockups. Magic resist + tenacity.
Positioning anddddd peel annddd side stepping. Play voli bear derp
ward his jungle camps. he has so many paths to gank from, but you will always see him at his jungle camp.
Items = 
Tactics = Kite, don't crowd up, CC, vision is key.
He can't 1v1 anyone unless he gets rid of the core need in his kit - health . He jumps in for teamfights. Use that as you will.
DoomRPG8/4/2016, 9:41:16 AMWhile im not a Zac player nor a great league player from my experince playing against zac the best way to fight him is to avoid areas that are common zac E areas if zac ganks you from the nth dimension in a specific spot, Dont go there unless Zac is somewere else on the mini-map (ganking bot or something) If your laning against a zac, Avoid his E Q combo if possible if you are melee, They deal the most of his burst damage and his W doesnt do to much right away and you should win the trade, if you are Ranged then bait out his E and once he uses it to initate you should be free to kite him even if he lands his Q
