Hello @jxde and welcome to the forum!
Have you already searched our forum and found this not working:
Although it is for the remote, it is somewhat connected to your zoom function.
And if it’s not that, did you already check if Krita’s shortcut settings for your zoom fit those of your tablet? You’ll find these under ‘‘Settings’’ → ‘‘Configure Krita’’ → ‘‘Keyboard Shortcuts’’
there it is found under the menu →
Action
→ Menu
→ View
Zoom In
Zoom Out
Michelist