Pros and Cons

Pros: - Ranged Champion, - Good Crowd Control with Time Warp, - Good Harras, - Chronoshift is OP, - Good Focusing, - OP passive.

Cons: - Squishy Champion, - High mana cost skills, - Low mana, - Only few skins.

Summoner Spells

is the best way. Why? Heal will bring you and your ADC Health, when you will get caught. Flash whereas is necessary. As support never use flash to save yourself! So when should you use it? Look at Chapter 6.

Items

I was trying to find best items for Zilean few times. And it worked! Boots of Swiftness will make you the fastest player on map and it is necessary for support, to be faster than opponents. Locket of the Iron Solari has got very good Unique Aura. If you want to catch up your opponent or run away, talisman of ascension is the best way. Mikael's Blessing's Unique Active allows you to run away when you get caught, or help your ally in teamfight.

Abilities

Best way to support as Zilean is harrasing. It's very powerful. Use Time Bomb and Time Warp fast, and go back. Do it few times and your opponent will be dead or very low. Best Ability Sequence:

Masteries

My option is good, but there are two good, too:
AP or...

Runes

Second option for support's runes:

How to Play?

I will present you few short actions with Zilean:
1)Bottom lane, 2v2, normal situation
- Run to your enemy,
- Use Time Bomb and Time Warp fast (harras),
- Run away fast.
2)Bottom lane, 2v2, your opponents are low
- Use talisman of ascension,
- Use Time Warp on your ADC,
- Use Rewind fast,
- Use Time Warp on your opponent,
3)Bottom lane, 2v2, you get caught
- Use talisman of ascension,
- Use Mikael's Blessing and Heal on your ADC,
- Use Time Warp, Rewind and again Time Warp,
4)Teamfight, 5v5
- Use talisman of ascension on all your allies,
- Run to wounded ally and use Mikael's Blessing,
- If someone get caught, use Chronoshift
5)It's teamfight, but you aren't there
- Use talisman of ascension,
- Use Time Warp few times,
- Use Flash if necessary to help your allies,
- Help your team.

WARNING:
If you want to play Zilean good, you must be very smart and fast.