If 2 Zhonyas are placed on a unit, do they proc one by one or at the same time when the unit would die?

Ruling: When a unit with two Zhonyas would die, you choose the order of the replacement effects. The first Zhonyas saves the unit and is destroyed, while the second Zhonyas does not trigger and remains on the unit.

Sequence:

• First Zhonyas replacement effect resolves, saving the unit and destroying that Zhonyas
• The unit is no longer dying, so the second Zhonyas does not trigger
• The second Zhonyas remains on the unit

Nuances:

• If 2 units die at the same time, both Zhonyas would be used to save both units