Can you have multiple Zhonya's Hourglass on the field at once, and if a unit dies, do all of them trigger or just one?

Ruling: You can have multiple Zhonya's Hourglass on the field at once. If only one unit dies, only one Zhonya's Hourglass gets used.

Nuances:

• Multiple copies can be present simultaneously
• Each death triggers only one Hourglass, not all of them