Hi
achromatic - big welcome to the forum.
Please go to the
KWiin > All Effects page and making sure the Zoom option is is enabled go to the right hand side off the Zoom line you should see an icon with a spanner on it.
Click on the spanner icon and it should see the image below

Now select one of the shortcuts and it should show two fields -
Default and the other is
CustomIf the
Default isn't to your liking choose the
Custom one
With the
Custom one enabled click on the button that says
None and you can now enter your own choice of shortcut keys
When done, press the OK button and hopefully it will work for you