@speedlite,
If the voltage does not exceed the USB voltage you can use any triggering device available in your locality.
With the current CHDK, you don't need a script.
The first press is a half press, the second press triggers the camera. (within a given duration; I think 2 seconds)
If you use SDM the first press triggers the camera.
Others may have their cameras set up differently.
I can't advise you on the zoom; that requires one of the gurus on this site.
