'zoom' [<scale>]|[<p1x> <p1y> <p2x> <p2y>]
This keyword is used to scale the model in the window. For example
will increase the size of the representation of the model by a factor of 2. A certain region of the model can be specified with two corner points of an imaginary rectangle. The coordinates are relative to the graphic-window which has its origin at the left/lower corner and as a fraction of the edge-lengths. For example
zoom 0. 0. 0.5 0.5
will display the third quadrant of the window scaled by a factor of 2.