Watch what the ADC does when you approach. Oftentimes you can E yourself out of a bush, startle the ADC, and throw your bombs right behind them. The bad part is when you go up against a ballsy Lucian who is not afraid of you, ignores the bombs you've just placed behind him, and then guns you down.

If you miss your stun in a teamfight and you already have your mythic item, remember that you can E them for additional damage.

Smart people will stop attacking those you ult. Use it as late as possible (but not too late.)

You don't have to double-bomb. If you throw your first and miss your second, you've wasted about 95 mana. Zoning and poking is perfectly fine.

You can double-bomb yourself if someone is standing on you. It'll hit them and stun them.

Dropping a bomb on the minion an enemy is just about to kill is a good way to safely smack them in the face.

Dropping your bomb on an invisible ally (Eve, Shaco, Rengar) makes your bomb invisible. Try it!

I've only recently gotten into Ranked but I've been playing Zilean for a long time. I've never liked the builds I find on here because I don't see the point in building items that don't do anything for your character. Ardent Censer, Staff of Flowing Water, and Redemption are great items--but they're not very good on Zilean. He's a mage with amazing utility built into his kit. He scales amazingly into late game and has an incredible laning phase. He is one of the highest damage supports and has some of the best mobility in the game.

Thank you for giving this guide a chance. I don't have a high rank to prove I know what I'm doing, but Zilean has been my main for a long time and I think he's drastically underplayed. (I also think people often build him poorly.) This is my first guide on Mobafire and I made this account to post this because I didn't like the guides I was seeing. Best of luck in your games!