I have an old Logitech mouse without mozsewheel. + and - didn't wordk for me, not even as I assigned them in the controls (looking at the keyboard controls within the game, the controls say that there aren't any keys assigned to zooming, at least in my games).

When you find a big kettle of crazy, it's best not to stir it.
--Dilbert cartoon

"Interplay.some zombiefied unlife thing going on there" - skavenhorde at RPGWatch