Zombies aren't exactly grimming up the Marvel Apes universe.
One of the MAJOR aspects of the series - a major aspect of this one-shot, as well - was that this is a world populated by APES.
Not funny cartoon apes, but savage beasts, whose idea of justice is to beat any criminal who doesn't become submissive to the alpha to death.
The Apevengers murder Doc Ook in the first issue (while Marty watches on in horror). The Invaders (minus the Human Torch) are vampires, who murder Reed Richards. And were going to invade the 616 universe for more blood until the Apevengers and Marty stopped them. Speedball didn't want to return, because he was marked for death for helping Marty. Spider-Monkey, at the beginning of this issue, was seconds away from vacuuming up Sandmonk, when Wolverine stopped him, because the dust-up was friendly. (And Spider-Monkey is one of the gentle simians.)
etc.
The Marvel Zombies series (particularly 1, 3, and 4) have a LOT more humour than Marvel Apes did (the humour in which, outside of the names, was restricted to the backups).