Thanks for the comment.
Not sure how farmilia you are with Unity/ C# but what it boils down to is.
Zoom - move along camera.tranform.forward
Moment - move along plane with normal camera.tranform.forward
Rotation - two parts:
convert mouse x movement to rotation on xz plane (global space)
convert mouse y movement to x rotation (local space)
Maybe that gives a rough image of how it works.