Zim - It is under 'Settings -> (Advanced) - > Keyboard Commands (or Shortcuts'.
Open that up - and you SHOULD be able to delete the commands individually by the bs-del method. Painful to go thru them all- and my suggestion really was tongue-in-cheek. I am not using the standard browsers (FF,GoolagChrome,IExploder) any longer- so you may or may not be able to disable individual shortcuts.
On the OS- not sure- and I don't really recommend it.
When one's mouse goes out, you gotta be able to navigate somehow - even if to only shut-down the 'pooter legitimately.
Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good ...