Okay so the only thing you need to know about jungling zac is the basics.

-Dont be afraid to gank early(pre 6 or before first back)
-Gank > clear jungle... if you think you can gank just do it. you want to create as much map pressure as possible. They wont tower dive your bot 6 times pre 20 if your constantly there.
-Damage is underrated, ei if you walk mid and harass their mid laner but dont get the kill your mid can now farm safer or control the lane and have kill pressure, even if you dont get an assist its still worth.
-Constantly watch the map and ping for your team if you see something
-While watching the map think about where you would gank your teammates, that is most likely where the enemy jungler is going to be, ruin his gank by being there.
-be there
-you need to just do it

Noone is a threat if you just use your brain. If you get invaded ping for help your passive will bait the enemy jungler.
"but my team doesnt come to help" - well then it sux to be you but guess what, zac only needs one item to create map pressure and your going to do that once you get that item... actually your going to do it before because you are... remember map pressure, who cares if the enemy is in your jungle because your just camping in their lanes