Maybe zoom is the wrong word for it. Orthographic scale might be a better term. I want the player to see more or less of the isometric/orthographic map.
When in 2d (with pre rendred isometric/orthographic graphics it was easy to just scale the layout.
gist.github.com/curran/4f4c6ef5dde876fca80906d5e5c13344
I'll test it top down as would be fairly easy. I'm guessing you are right though :)
Screen shots examples of desired effect:
Looking at an camera angle and moving the camera away and closer to the player is some fairly hard trigonometry to implment in Construct