Does the Zero Drive have to be un-equipped to use its Banish this: play all units banished with this" ability?

Yes, The Zero Drive must be unattached to use its ability that plays banished units.

According to the card's text, the ability is restricted to when the equipment is unattached. This is supported by RiftJudge FAQ #6043, which clarifies the interaction:

• "You cannot use Zero Drive's ability while it is attached to a unit."
• "This applies to all equipment - their additional abilities cannot be used while attached to a unit."

Regarding the movement of equipment when a unit leaves the board, Rule 435.1 states: "When an un-attached Gear is created or played at a battlefield, or is at a battlefield for any other reason, it is Recalled to its controller's base during the next Cleanup." If a unit equipped with Zero Drive dies, the equipment becomes unattached and remains at the battlefield, at which point you can activate its ability.

Note: I could not fully verify the specific card text or the timing requirements regarding the cleanup phase against the retrieved rules.