Zoom doesn't really make sense with an orthographic projection. Normally moving the camera forwards and backwards makes things bigger and smaller with a perspective projection. But the whole point of an orthographic projection is that nothing changes size when you do that, so you won't see any difference.
The editor uses a 2D stretch to implement zoom with an orthographic projection as zoom is useful for editing, but in that case it's not actually moving the camera, and I don't think there's a good equivalent if the camera is not pointing down 2D style.