If Zero Drive banishes a unit as a deathknell and Karthus is in play (adding a second banishment trigger), can Zero Drive play two copies of that unit later when its ability triggers?

Ruling: While Karthus does add a second banishment trigger, the second trigger cannot reference the unit because it was already moved by the first banishment. Only one copy can be played later.

Sequence:

• Both banishment triggers go on the stack
• The first trigger to resolve banishes the unit
• The second trigger resolves but "whiffs" because it cannot reference the unit that's already been moved

Nuances:

• "Banished by this" is a binary state - a unit either was or wasn't banished by a specific effect, it doesn't stack
• The card must exist in the banishment zone to be found and played later
• Similar interaction occurs with Ekko's deathknell: if Zero Drive and Ekko's recycle trigger both occur, whichever resolves first makes the unit invalid for the second effect