If an opponent uses Possession to take control of a unit, and the original controller has Zhonyas Hourglass in play, does Zhonyas Hourglass prevent the possessed unit from dying while under the opponent's control?

Ruling: Zhonyas Hourglass does NOT prevent the possessed unit from dying while under the opponent's control, because Zhonyas Hourglass only affects "friendly units" and the possessed unit is not friendly to its original controller at the time of dying.