Monsters from a monster zoo that are resurrected don't make the "monsters left in the zoo" counter go up, but they make the counter go down when they die. i.e. if you keep killing the same monster over and over again, you can complete a monster zoo without killing anything else. Running version from Steam for Linux 64-bit
I've noticed this too. Running via Steam on Windows 10, but I'm pretty sure I noticed it in previous Windows operating systems as well.
