Nitrosol here.
Revamp for this guide coming soon in light of a few recent changes during a short hiatus of mine.
The removal of mana from Zhonya's makes archangels staff infinitely less useful and makes mana starvation a more pressing issue. The removal of Sage's ring is also nice, seeing as how you can begin getting mana in smaller, quicker installments when building CD reduction (Frozen heart/Glacial Shroud).

Your guide is pretty good. I play Zilean too, he is really funny. My Itembuild is like this:
1. Sapphire Crystal -> Tear of the Goddess
2. Boots of Speed
3. Amplyfying Tome -> Mejais Soulstealer
4. Boots of Speed -> Boots of Swiftness
5. Tear -> Archangel's Staff
6. Rylais
7. Zhonyas
8. Something like more AP or Armor ... Depends on the situation.

After reading your guide i think i will switch Mejais with Deathfire. Makes more sense. Ill give it a try.