UNDO/REDO are very powerful commands, until it comes to zoom and pan. Do I really want to undo/redo every little zoom or pan? NO!
In previous versions of AutoCAD, ADT, or ABS, the UNDO/REDO command applied to each instance of zoom or pan. In a typical drawing a user zooms or pans around hundreds of times, there is no easy way of undoing or redoing a string of consecutive zooms or pans.
Now in AutoCAD, ADT and ABS 2006 the ZOOM and PAN command can be combined into one UNDO/REDO. You can use the new "Combine zoom and pan commands" which is located in OPTIONS. This will combine consecutive zoom and pan operation into one, so you can UNDO/REDO in one step.