Can an opponent force a hidden Zhonya's Hourglass to save a specific unit (Poro) instead of another unit (Blitzcrank) when multiple units are dying?

Ruling: If multiple units are dying simultaneously from combat damage, the Zhonya's controller chooses which unit gets saved. However, if the opponent uses a spell to kill a specific unit before combat, they can force Zhonya's to save that unit instead.

Sequence:

• If all units die simultaneously from combat: Zhonya's controller chooses which unit to save
• If opponent plays a kill spell on a specific unit (e.g., Poro) before combat: That unit dies first, and Zhonya's must replace that death if activated
• To force a save on a specific unit during spell resolution: Opponent casts kill spell on primary target (Blitzcrank), controller flips Zhonya's, then opponent responds with another spell targeting the unit they want saved (Poro). The most recent spell resolves first, killing the Poro which gets saved, then the original spell kills Blitzcrank

Nuances:

• Since Zhonya's is hidden, the controller can choose not to activate it in response to the first spell
• Units dying at the same time (like from combat damage) give the Zhonya's controller choice
• Zhonya's does not target