Zilean just isn't fun to play against
Now he is not OP, mind you. Not by a long shot. He may be a bit balanced actually (though I don't play him much in depth so I can't say).
However, his kit is just unfun to play against.
Let's try to take a closer look
-Passive: The enemy ADC now is a level ahead of you. Congrats they get their ult first. Gl -q: May be hard af to land, but despite the fact that I was probably outplayed, it sure doesn't feel like it. His bomb stun feels cheap. -w: A part of me wants to hate this ability, but in all reality, its fine. e: Probably my least favorite part of his kit. Nothing like getting practically snared for around 4 seconds. Or getting the enemy to charge at you with the speed of a sion ult. I really just don't like the versatility and the amount of potency this has. Probably the worst part is that he needs this ability to be anywhere relevant. r: Nothing like a lose-lose situation. Zilean ults the ADC I now have three options
1: Run from the ADC now, even if they were at low HP, because they will kill me within that period that they have the hourglasses around them 2: Try to continue fighting while an ADC is mowing down your team 3: Kill the ADC that is at low HP and watch as it revives with their full health bar.
Again, I can't say that Zilean is OP, just that I hate what his kit does inherently and that it isn't fun to play against. And when you win against a Zilean, it's almost always a stomp against him, which isn't much fun either, unless you have some vendetta against Zilean, which I for one don't.
EDIT: I'm not asking for ways to beat Zilean. I win most matches against him anyways. It's just a pain doing so that I have a problem with.
Learn the old man before snapping at em.
or 