Can a Hidden Zhonya's at one battlefield be flipped to save a unit during a showdown at a different battlefield?

Ruling: Yes, a Hidden Zhonya's can be flipped from one battlefield to save a unit at a different battlefield. When flipped, it immediately recalls to base, and since it doesn't target, it isn't restricted to the current battlefield.

Sequence:

• Zhonya's is flipped from its hidden battlefield
• It immediately recalls to base
• From base, it can save any unit at any battlefield

Nuances:

• This applies to Hidden cards generally, but with restrictions: Hidden cards can be flipped at any time you can play a reaction, but if the card has to target or is a unit, it must be played to/affect the battlefield it was hidden at
• Zhonya's works across battlefields because it both recalls to base when flipped AND doesn't target a specific unit