To review: the Martian Zookeeper requires a Cow and a male and female Human, but ties are broken by whoever has more total Humans. So if player A is all set to win when they play the Goal, but B also meets the conditions, with more Humans, but they’re hidden in the Abduction Chamber, can player B reveal their Humans and win?

A: It’s going to depend on how quickly player B realizes they could prevent the win by releasing their Humans. The Abduction Chamber can be accessed at any time, but it’s not retroactive. I might choose to set my Humans free during another player’s turn, but I’d better be prepared for the possibility of the Martian Zookeeper Goal coming up, since BOTH of us have the win conditions, and it’s going to come down to a head-count of our Humans. I’ve got to release them right away so they can be included in the tally.

If player B realizes they need to release their Humans after they realize player A has won, then they realized too late.