Center: specify Center point and Magnification or Height (a smaller value for the height increases the magnification)
Extents: same as SolidWorks Zoom to Fit; fits all objects into the current view
Scale: specify Scale Factor (2X doubles current image; 0.5X makes it smaller)
Window: specify First Corner and Other Corner
Previous: returns to the previous view
<Realtime>:
The pointer changes to 
. Hold the pointer down anywhere in
the window and move the pointer up to increase magnification, down to
decrease magnification. To exit from the command, press Enter
or Esc.