A: I prefer the definition of office plankton.
B: These are different concepts.

Office plankton is the food for corporate fish larger. Each of us at a certain stage of the career is at this stage, rarely someone is taken immediately as a boss.

A corporate zombie is a guy who has lost interest in work, his spark is extinguished. He does everything automatically, not including the mindset. You may not even give him tasks. I know the case of a guy who went to work for 2-3 years, no one gave him almost any tasks, but he did something behind his PC, quietly sat in the corner, went to drink coffee to the machine. Per he still works there.