Thanks for chiming in waterwingz.
No, just using click "zoom_in" doesn't crash the camera when running as a normal script, the lens do zoom in and the zoom lever does work afterwards. It doesn't run at all when set as a startup script.
Now, running any of the preceding scripts causes the camera to execute all the commands just fine but disable the zoom lever, most of the times! On some occasions it just crashes the camera after executing the commands.