Can The Zero Drive revive a gear unit banished by its effect?

No — once it's in Banishment that card is a plain Gear card, not a unit, so Zero Drive's "Play all units banished with this, ignoring their costs" can't pick it up.

The "gear unit" status (e.g. from Lady of Clockwork or a "gear become units this turn" effect) is an applied layer effect that only exists on the board; changing zones to Banishment makes it a new object and clears that type change (Rule 124.1), and card type is evaluated in every zone (Rule 148.2.b). Same reasoning as the established Temporal Breach + Orianna ruling: it comes back as ordinary Gear, not a unit gear. So the banished card sits in Banishment permanently.

The exception is a card that is printed as a Unit and also has the Gear type (Rules 177–178) — that one is still a Unit card in Banishment and does get played, entering at your Base as an unattached Gear.