This is a zac build that deals a lot of damage and has a lot of mobility with around combos.
You have punishable early game but mid game you are almost strongest character in jungle know that and play with that.
BUILD ----
With this build you gotta care for your clear and tempo you are gonna buy bamis fire first item no mattter what if you have extra 350 gold you can build dark seal. After bamis you go hextech (BUY DARK SEAL INSTEAD OF 400G BOOK FIRST IT GIVES A LOT OF SNOWBALL CHANCE) After you build hextech you need sunfire %90 percent of the games but if enemy has mostly ap damage you can build radiant as well after that you need spirit visage 3th item spike is insane because of visages passive %25 heal++. Buuuutt if enemy has no ap you can go randuin or thornail 4th item you can go randuin thornail jaksho or abysall mask all your choice (if you want more damage abysall or upgrading your dark seal to mejai is also a good choice). As boots you Ionias are pretty good choice for zac a lot of games you wanna go ionias but if enemy has hard cc you gotta go mercs or you cannot play zac you can also go tabis if enemy has hard AA enemies but i highly reccomend ionias almost every game. Thats all about build.
Gameplay---
As i said your champion is weak early game you just go full clear and remember your champions clear is not good as other champs. Mostly go for top to bot path its more valuable (in some scnerios you can look for mid gank DONT GO FOR TOP - BOT GANK LVL3 NOT WORTH its risky to gank lvl 3 mid cuz it gives a lot of tempo to enemy jg and enemy jg can invade your buff only go for lvl 3 mid gank if you are sure thats a kill)
after you do your clear you can look for ganks lvl 4 if cant look for ganks and enemy lanes has prio go for the other crab just dont risk it. You have a good scaling look for ganks but dont try too hard just wait your item after and try to get first drake fast after your first base (if can) stacking drakes are pretty good. After your first item you can look for plays more often. Play for Free ganks or objectives. Its all you have to do
-----Play Safe Wait For Your Spikes Make %100 plays you dont have to risk it care for your tempo Play for obejctives-----
Ban----
Just ban janna
(thresh poppy is also an option DONT BAN JG CHAMP)
Tips-----
Enemy is not gonna expect your q flash right click into r use that to reach their carries and start fights
You dont have to jump into their faces you can also jump behind them to close the gap and dodge ccs
Trust you heal factor and trust yourself know your damage
Thats all thanks for reading by Recep İvedik-Fntas will answer your comments