Zac's auto doesn't do much so when chasing run beside spamming W
Use your E to instantiate smart fights, beware of who you are ganking and who will back you up
Don't gank before you are ready and remember, no matter how much flame you get you will always struggle ganking super fed lanes because they will be able to 1v2 you.
Zac has no mana no energy ect. so you need c/d reduction, don't be silly follow my runes or make your own variation on them but just remember, it cant be changed in game. so if you choose bad ones and are all like i wish i had more cdr or MR then you will regret it and probably lose the game, don't be that guy.