Canon zoombrowser

It's not zoom browser that downloads from the camera,
It's Canon camera window, just a driver that allows windows to detect a camera when you plug it in. The camera window asks if you want to view the files in the camera flash drive, or download the files in the camera to zoom browser or to another location.
Actually, deleting all the zoom browser existing software, delete multiple camera windows, and other cannon software, restart the computer, plug in one canon camera, see if windows detects it. Windows should detect the camera flash drive when it is plugged in. Windows should offer to open the drive and view the files. You should be able to save what is on the camera drive to: "my pictures"
Later you can move the photos saved in my pictures to: zoom browser, after you install ONE zoom browser.
Plug the second camera in, windows should detect that too. Again, save files in camera to my pictures.
Installing ONE zoom browser, after you have deleted all older versions and restarted, should then be installed with the anti virus or any security turned OFF.
Download the latest zoom from the canon website, and any updates that are available for it.
After you install zoom, and detected both cameras, turn the antivirus back on.