In Whimsical, one of the options for zooming in and out on a board is to hold down "command" (on a Mac) or "control" (on a PC) and then scroll using your mouse.
Default (similar to Figma & many others):
Holding "command" (on a Mac) or "control" (on a PC)…
Inverted (similar to Sketch & Adobe XD):
Holding "command" (on a Mac) or "control" (on a PC)…
You can go here to invert the zoom directions (not currently linked to in the app): https://whimsical.com/settings