Implement zoom in standard assets free look camera

I’m using the free look camera from the standard assets and i want to implement a zoom functionality.
The Problem is that i can’t influence the localPosition of the camera and if i change the position of the camera rig the pivot moves and i don’t want that. Is there a way of keeping the pivot at the Targets Position while moving either the rog or the camera?

If your camera is orthographic you can change the camera.orthographicsize and if your camera is perspective you can change camera.fieldOfView.