[unknown]
I can only view pictures and menu on Zoom if I turn on the camera by the "Playback" button.
Unfortunately, your camera does does not support HDMI out in shooting mode. Only the EOS M can a couple of the G X series do. CHDK is not currently able to add this functionality to cameras which do not support it.
The only ways you could use your sx700 as webcam would be to use the analog video output (with Canon AVC-DC400/ AVC-DC400ST compatible cable) and an analog video capture device (google easycap for a cheap example), or using chdkptp live view, and capturing with the window with something like OBS or some virtual webcam software. Either of these would only give you low quality SD video.
