Zilean Runes explained
There's one set of runes for Zilean on patch 15.2 that is the clear favorite for LoL players and pros alike. The best Zilean rune paths on the position 
Support are 
Resolve as the primary path and 
Sorcery as the secondary path with a pick rate of 50%. Besides picking runes on Zilean you should learn how to play Zilean and if you are interested in pro matches take a look on how a pro builds Zilean. If you want to discuss 
Zilean then you should visit the champion subreddit.
Zilean runes from primary path
Resolve empowers the survivability of Zilean and increases the tankiness. Most of high elo players – and our LoL pros in the the major regions – have agreed that Guardian is the best keystone rune to run on Zilean. This keystone rune grants a shield to your teammate and towards your own, as soon as one of you gets damage by an enemy champion. Other primary runes on Zilean are Demolish, Conditioning and Overgrowth.
Demolish increases your pressure on the enemy turrets. This rune will help you to punish bad roams or backtimings of your lane opponent. Conditioning powers up Zilean tankiness after the laning phase. Overgrowth increases your maximum amount of health.
Zilean runes from secondary path
When it comes to your secondary path, most Zilean players prefer to go with Sorcery. Sorcery empoweres abilities of Zilean and increases the available champion resources. On the Sorcery path, the best runes for Zilean are 
Transcendence and 
Manaflow Band.
Transcendence for some more Ability Haste. This is usually followed up by taking Manaflow Band for additional mana and mana regenaration.
FAQ for Zilean Runes
Which is the best keystone rune on Zilean?
The best keystone rune on Zilean is Guardian. This Zilean runes setup is then referred as Zilean Guardian.
What runes does Zilean use?
Runes from the paths Resolve and Sorcery are the most used runes on Zilean. For the exact pick rates of Zilean runes used, you have to study the rune distribution presented.