Hi Marko. Thanks for your insights. I can see what's going on now. Both your code and mine fails to do a Zoom Extents outside the document that the code was run from. I attempted using (vla-sendcommand doc "_Zoom e "), but it seems there are asynchronous problems with this. I will keep playing around with it.
Your script version would be fine in certain circumstances, but I think the OP wanted a more general solution without having to move documents around.