1 that action should be the arrow keys not the mouse... has your keyboard got some keys remapped?
2 the default Z is for whatever action is in the first action bar square... that could be Jump or anything else

it sounds like the problem is your keyboard try going into your game options, keybinds and clear the 2nd camera left... save changes and test if your mouse + alt still runs off
[Linked Image from gog.com]

Luke Skywalker: I don't, I don't believe it.
Yoda: That is why you failed.