i have an '08 X5 and did not have the hitch installed from the factory, and did not have the zoom function on the camera.
When i recently installed the hitch and harness, i had to have the dealer program the harness, and the zoom feature now appears.
It is something with the programing, or the software version that your particular truck has.
this feature makes backing up to the motorhome a peice of cake.
Right on everytime