Can you play a hidden Zhonya's from a battlefield in response to a Deathkneel trigger during combat cleanup to save a different unit, and what happens to the Zhonya's?

Ruling: There is no clear window to play Zhonya's from hidden during combat cleanup. According to the rules, no Focus or Priority is passed during a cleanup (320.1), which would prevent playing the hidden Zhonya's in response to a Deathkneel trigger. However, there is debate about whether priority is gained between the Special Cleanup and the "clear contested status" step (440.1.b) of Combat Cleanup.

Sequence:

• Unit dies during combat, triggering Deathkneel
• Special Cleanup occurs (which includes regular Cleanup procedures)
• During Cleanup, all gear at battlefields is recalled to base (322.5)
• Hidden cards at battlefields not controlled by the same player are removed to trash
• Contested status is cleared (440.1.b)

Nuances:

• Some interpret the rules to allow priority after Special Cleanup but before clearing contested status (312.2.c), which would allow playing Zhonya's while the battlefield is still contested
• This interpretation is disputed and likely not the intended interaction
• Hidden units must be played to their battlefield, but gear (including Zhonya's) is always played to base regardless of where it was hidden
• The question has been submitted for official clarification but no response has been received yet