btw, this seems to be a very old problem even on regular Opera that was never addressed: https://forums.opera.com/topic/13392/how-do-you-disable-scroll-wheel-zoom

The ⌘⌥+scroll shortcut for zoom is being triggered automatically all the time because of scroll inertia

When I change tabs with ⌘⌥→ or ⌘⌥← right after scrolling the page, both the previous and the current tab are zoomed in or out (depending on the scroll direction)

There's no option to disable that shortcut in settings. This is a Opera (Air) specific problem...no other browser in macOS uses that shortcut.

It should probably be disabled by default on mac, but at the very least it should be possible to disable that shortcut.