I've been playing zilean for the same amount of time i've been playing League 4 years, i've racked up 1.6 million mastery exp on Zilean. I'm a support main at heart but just recently felt the need to switch to top lane and show the world the power of zilean.

zilean's early game is kinda **** until lvl 3, sure you can bomb people back to the stone age but landing the right bombs tend to be somewhat challenging on good opponents. so keep poking out with bombs (from a safe distance) then once you hit level 3 you can be a little more risky (not by much) the trick is you make you opponent underestimate your combo so you let them push towards you (when your jungler is on your side of the map) but most of the time in top lane its vs melee fighters so zilean tends to uber push these champs under tower.

Zilean's ganks and roams are pretty ubsurd with zileans E speed (or slow) makes landing the Q+W+Q combo really easy. Zileans slow max rank is 99% slow even at lvl 3 its 75% (so typically i like to max bomb then put my E at rank 3 then max W.) Teleport with zilean can be really fun because lets say your jungler is unsure of ganking well you tp speed that sucker up and when he/she goes in you stun whomever they are going in on.

so by late game you should be sitting somewhere close to 5K health. your double bomb combo will kill any adc (try to pick these guys out for your team) oh yeah don't worry about assassins they can only get through maybe half your hp pool (if you're playing smart) XD with warmogs you should not have to use your ult on yourself, but i understand things happen so always be aware of who to ult. if you have a master yi on your team (safest bet is to tell him to run in and ult him, if he's smart he will have GA. so he can die come back to life only to die and come back to life again all the while youre killing the enemy.)