Let me put it to you this way... Rewind Bombing is better if I can deal more dmg early game. The more Mpen I have early the more dmg I do when there is little MR.

Magic Pen is of course always useful, but with Zileans 90% AP return, you'll get a much better rate of return using AP wherever you can instead of Magic Pen. Marks are the only place I'd take Magic Pen since they're primary there.

Cuz ppl dont like too much of Zilean. He's not the most popular of champs

For such a great guide, why is there only one vote?

You should post it anyway lol I wanna see how you did. Remember support isnt about kills lol Its about assists.

As for team fights, do the ninja thing. Drop a time bomb, get into the brush, go around the other way, time bomb, back into the brush. Use speed buff on you to make sure that you get some distance from chasers... also make sure you have wards or minions you can port to. That will make things better for you if you need to get away.

Even though I really sucked overall I had some good fun playing this build.
I did a sneak attack on a Lux at half health at her turret, snuck behind her, Time bomb, Rewind, Time Bomb, Ignite. I didn't even watch her die, just casually walked/floated away. 5 seconds later.... ADONIKAM HAS SLAIN LUX.. MUWHAHAHAHA!
The enemy team also raged at me whenever I speed boosted a team mate away or bought them back to life. Which led to me being focused ALOT. So basically my greatest failure was in the team fights. I could ever get close enough to time bomb and most likely die or try to speed boost/slow or even try to bring my team mates back to life.
I decided not to put up the screen shot because it was too embarrassing but I bought Zil so I WILL PERSEVERE and try him again.

EDIT: Take a look in the Theory Crafting section in the forums at my idea.