With the rules change, does Zhonya now work at reaction speed for any unit on the board regardless of where it is when played from hidden, with no constraints on what it saves?

Ruling: Zhonya has no constraints and saves the next unit which dies, regardless of where it is on the board. When played from hidden, it works at reaction speed for any unit.

Nuances:

• You cannot react to a unit dying. You must play Zhonya before the unit is dead, or Zhonya will be trashed along with your hidden cards.
• Zhonya resolves instantly as a permanent and cannot be reacted to, though opponents can still react to the effect that would kill the unit.