Hey, im Dreezi from EUW and im Gold 4 at this moment. I made this guide to open your eyes for Zac toplane. In my opinion hes at Sololane really strong because of his massive poke + sustain. Have Fun with this Guide!

Pros:
Great Engage Potential
Strong peel for your Carries
Big Basic Damage on his skills
Extremely strong sustain
Hard CC

Cons:
Hard to Master
Ultimate can be fail-used by throwing the enemy to your squishys
While your ultimates on you can get thrown away.(Xin Zhao R)
Passive can get break easily

You will always be the guy who engages(mostly). So if you make wrong decisions it can be bad for your team. In teamfights you can:
1: Hold the enemys Carries away from the fight alone while you should be careful on your own.
2: Peel for your whole team while helping at killing the Opponents.
3. Cut enemy Tanks away from the fight(hard to do).
As Summary your Team really needs you in fights. And even if you would die you have your passive who gets most times protected from your allies.

Can be hard if you spam your skills and push too hard. Just try to hold your skills for the lane opponent and for ganks ready.