Zoom function of external camera

The external camera can connect but Prezi use the default settings and ignore the zoom that is set with the external camera. When using webconferencing, the zoom of the external camera works without prezi but when I select prezi as the camera the external camera reverts to its default setting.
How to get the zoom function of the camera to work ?

Hi @Joseph_Gil, Could you please tell me the exact brand and model of the external camera that you are using?
In which application are you using this camera with its zoom feature? Do you have a separate camera specific application where you set the zoom level?

Could you also tell me if you are using Windows or Mac?