If Icathian Rain kills a unit protected by Zhonya's Hourglass before all instances of damage are dealt, can the remaining damage instances target and kill the same unit again after it's saved?

Ruling: Yes, the remaining Icathian Rain damage instances can continue targeting the unit after Zhonya's saves it, potentially killing it a second time if enough damage remains.

Sequence:

• Icathian Rain deals damage instances one at a time
• After each instance, a cleanup step occurs
• If a unit would be killed during cleanup, Zhonya's replacement effect saves it (moving it to base and clearing damage)
• Remaining Icathian Rain instances continue to target the saved unit at its new location
• If enough damage remains, the unit can be killed again

Nuances:

• The damage instances are independent, like homing missiles that maintain target lock
• Zhonya's is a replacement effect, not a triggered ability, so the unit is never actually killed (just "would be" killed)
• If multiple units would die simultaneously and Zhonya's can only save one, the owner of the units chooses which one is saved
• Damage is cleared when a unit is saved by Zhonya's