How does Zhonya's Hourglass work when a unit would die during battlefield resolution?

Ruling: When a unit would die, Zhonya's Hourglass saves it by sending it to base instead, and Zhonya's is placed in the trash.

Sequence:

• Calculate battlefield might totals
• Determine winner and which units would die
• If a unit would die, Zhonya's triggers: send that unit to base and place Zhonya's in trash
• Other losing units go to trash normally

Nuances:

• Zhonya's is not attached to a specific unit beforehand
• If multiple units die simultaneously (like from combat damage), the owner of Zhonya's chooses which unit to save
• If the unit dies before combat damage is calculated, the saved unit's might is removed from the battlefield total
• If the unit dies to combat damage, you still lose the battlefield but keep the unit alive