I mean, he can save stupid teams from being out of position, he can zone like a mad man in bot lane and doesn't require much itemization to be effective.

Is he viable in lower elo? I know he can't carry, but he sure can win a stupid bot lane

Zilean is viable in every elo if you play him well enough.
Optimal is another story.

bamp

He's viable but if you are trying to carry yourself out of low elo zilean might not be the best champ because he lacks late game damage and his ult is pretty useless if everybody on your team sucks xD.

Either mid or top.. zilean ishh a good pick. He is not really good for being support compared with the main support champions 2000 + elo players are using.

You can play zilean up to 1700 elo as mid or top. Zilean does great damage on his e + double bomb combos. This combo takes 1/3 hp of mid lane mage/ 1/4 hp of tanky top laners with less mr at least. (The only problem is that if u know how to play him well... Dont waste ur ult on the wrong target ever or miss it to save anyone. Build much mana so u can always use ur W and keep ur ult rdy. )

Late game zilean does great damage... his ap:damage ratio is good... especially after his w reduces his bomb cooldown to few seconds around. You spam your q and slow/speed up like a boss with the help of ur w and sufficient mana in team fights late game. It's so much damage and so much help to ur team fight if u can do it properly.

Zilean isn't a great support unless you're playing against a 0-sustain lane with low kill potential. (there's no such thing, except for maybe Vayne+something like Zyra)

Of course Vayne Zyra has kill potential at 6, but by then you have anti-kill potential.

Any other lane, I would be very unhappy with a Zilean support. I love going against Zilean supports though. They make good gold sandwiches.