Does Zhonya's trigger automatically when the next friendly unit dies, and can you choose not to trigger it?

Ruling: Zhonya's triggers automatically when the next friendly unit would die. There is no choice - you cannot choose not to trigger it.

Nuances:

• Zhonya's triggers when a friendly unit dies, so if an opponent's Super Mega Death Rocket targets an enemy unit, it would not trigger Zhonya's unless the SMDR effect causes your own unit to die
• This applies even if Zhonya's is on your base