I have tried this (vla-zoomextents (vlax-get-acad-object)) and it works nice.
However, as mentioned it applies to active viewport only while I have multiple drawings opened at the same time of which viewports I want to set.
So I guess I cannot use this method unless I set sdi to be 0, which means I cannot have multiple drawings opened so I have to do it one by one.
One way I can think of is use .scr.
Do you have any other suggestions?
Thank you