Reminder that Zilean's passive is useless
Any ideas?

Any ideas?

Make it global and its fine /sarcasm Well, it allows your ADC get his level 2/3 a bit faster and that could help in early all-ins or trades... but Zilean is bad for all-ins/trades at low levels anyway
Zilean and nearby allied champions gain 8% additional experience from all sources.
Doesn't seem too useless.. i remember playing top lane and there was a Zilean at botlane.. and I remember getting the passive. Guess Who leveled up faster, got ult, Went all in and started snowballing, reaching level 18 quickly... Ahh goooood times..
It levels you up about half a wave before your opponent, and has literally zero effect at endgame.
Leveling up before your opponent isn't useless, it tends to put you at an ~80 HP advantage, ~3.5 AD and armor advantage, ~56 base-ability-damage (~25 AP), ~40 Mana, and some minor HP/MP regen and AS bonuses.
If you compare the bonuses to itemization, you actually get more than 1,000 gold's worth of stats per level-up.
Out-leveling opponents is powerful enough you don't run duo top-lane in the meta.
It's also powerful enough to give a substantial advantage to a team with 1 leaver in ARAM, winning 4v5s. Even though it's another map, pretty solid testament to EXP and levels being a huge deal if running with a man down is actually more than compensated with EXP gains, to the point it's an advantage.
So - not useless. You just need to push those windows with a 1k equivalent in gold bonuses on the Zil-master to make it count.