User blog comment:Willbachbakal/(Champion Rework) Zilean, the Chronokeeper/@comment-24385282-20160411212547/@comment-1330314-20160412063615

I assumed that the baseline rule would be that any ability with a cooldown would go on cooldown once cast, but you're probably right that I should specify that it also applies to casting them through Borrowed Time here.

I feel that, if Zilean imposes 3-second kill windows on his enemies, that's fine, because he's squishy enough that he can easily die well within 3 seconds, particularly with the above ultimate, which doesn't provide healing. Ultimately, the effect does provide strong CC when used right, but the CC itself is only momentary, and offers a lot of freedom in between.

Putting aside the fact that Time Warp has a little delay, the movement speed slow is relatively low compared to what you'd usually find on a mage or support, and the ability itself is only most effective when used in the middle of combat, not as an escape. Besides, live Zilean can apply a 99% movement speed modifier to himself and his target right now, which persists for seconds regardless of where you cast the ability, and can still get caught fairly easily. I think it's okay for such a squishy champion with low overall damage and unreliable utility to have situationally powerful crowd control. You're probably right that it might not be the best idea to use Borrowed Time to chain-CC targets, so I'll move Time Bomb's double-cast immunity to the passive and make it generally applicable.