[Replace the ALT key with CTRL]

I've been struggling to wrap my head around this problem too.

Yes it is a problem, because other application that i use daily (Blender, Davinci Resolve, Fusion, even DAW like REAPER) OOTB used Cmd + Mousewheel to Zoom In/Out. Intuitively it is like a standard convention.

Currently only Affinity Designer/Photo use Alt + Mousewheel to Zoom on my system. Thus, every single time i need to zoom, i end up rotating my canvas instead. It is very tedious, to reset to rotation (because it is also NOT undoable, not something easily reverted with a common keyboard shortcut). Zooming In/Out is a something we all do most of the time in Designer anyway, it's used more often than rotating canvas.

A very common most used task such as Zoom In/Out with wrong mouse modifier often make me lost my train of thoughts, because i have to set and remember another keyboard shortcut just to reset the rotation or diving into menus searching the right command to reset the canvas.

That is a very poor user experience.

If it's something idiosyncratic to the way Designer/Photo designed/programmed, at least give users the options to swap Cmd vs Alt as modifiers to Zoom / Rotate canvas.