If anyone out there is using Autohotkey and wants Windows Magnifier to treat the mouse wheel like it does the Plus/Minus keys on the numeric keypad (whether or not your keyboard has one), you might want to try these lines in your script, or use them in a script of their own.

LWin & WheelUp::Send #{numpadAdd}
LWin & WheelDown::Send #{numpadSub}

I wanted to zoom in and out at will, and not have to take my right hand away from the mouse wheel to do that.

This is a work in progress. If someone has other ideas to make the script better, please post them.