Moves the viewpoint towards or away from a selected port.
Multiport- Check to display the effect of a zoom in another view port. The first digitise selects the display port, the second and third define a zoom window in another port.
Defaults - Check to return the selected view ports to their default scale and position.
In - Zooms in on the selected view ports by this factor. A factor of less than 1.0 zooms out instead.
Out - Zooms out from the selected view ports by this factor. A factor of less than 1.0 zooms in instead.