How to pan and zoom and still keep 4:3

If your project settings are 4:3, your pan & zoom will be also.

You can also have much more control over panning and zooming if you manually keyframe your motion path in the Applied Effects/Motion settings rather than use the very limited Pan & Zoom tool.

I'm not sure.  It might help if you gave the source of the 4:3 clip and your project settings.   (I don't have any 4:3 video to try it.)