Can you react to Zhonya's being revealed as a hidden permanent before it resolves to protect a unit?

Ruling: No, you cannot react to Zhonya's being revealed. Zhonya's is a permanent and resolves as soon as it is finalized to the chain, providing no window to react to it being played.

Sequence:

• Player uses Hidden Blade from hand as an action
• Opponent reacts by revealing hidden Zhonya's
• Zhonya's resolves immediately as a permanent
• No opportunity exists to react with another Hidden Blade before Zhonya's protects the unit