I Propose a small buff to Zilean's Q.
Make it like this:
If another bomb is within the blast radius of the first bomb when it detonates, both bombs will be detonated and enemies inside both areas will be stunned for 1.1/1.2/1.3/1.4/1.5 seconds. (picture GP barrels sorta)
This makes it easier to land a stun on enemies, because people will usually stay away from you when you land one on them.