A defamation action by Zimmerman (BTW, wasn’t that the original name of Bob Dylan?) would name as defendants both the corporate entity NBC, and the individual producer directly behind that segment (and maybe some additional individual John Does.) What NBC is doing by firing the guy is attempting - with regard to itself only - to negate the “actual malice” element required to prove libel against a public figure. Thus, in the likely event of a suit, NBC will argue: “We accepted in good faith this segment as an accurate representation of the 911 call, but were deceived by this rogue producer (who previously had a good track record).”
In this way, NBC may rely on a narrative of a rogue producer who did commit defamation, in an effort to exculpate itself, NBC, of the charge of defamation. And no doubt, that’s why the producer & NBC will be represented separate counsel.
LLS