Love the backseat lawyers who will rush to judgement without having any idea what role Carmack played, what kind of agreements may have been made between Zenimax and Occulus, and whether that NDA was amended or replaced.
Guess what? None of us know right now! It would be a pretty huge blunder not to resolve a NDA.
Everyone booing Zenimax right now doesn't have a decent grasp on employment contracts and NDAs for intellectual property. If Carmack (or whoever) didn't go through the proper process for clearance, and it's proven that Zenimax substantially invested resources for Carmack to pursue Occulus development (which realistically shouldn't be difficult to prove), then Zenimax deserves every penny they are owed.
If otherwise, then of course not - but until we know the further details of such (which likely will never be disclosed), there's no way of really knowing. This story is about how you manage your employment contract, not corporate greed.
Throwing Zenimax under the bus just because it's generally easy to hate on the greed of corporations is rather unfair, even if in multiple cases elsewhere it is justified. It just might not be the case for this one.