Could not change view mode while sharing file as Host

I facilitated two Zoom meetings recently.  In the first meeting, the presenter shared her own files.
In the second meeting, the presenter needed me to share her files (which I had on my desktop).  I recorded the Zoom session in both cases and wanted to be able to resize the shared file portion of the screen and the speaker's portion of the screen.  In the first meeting, I was able to do that.  i.e. I could make the speaker occupy about 60% of the screen and the file was shrunk as a result to about 40%.  In the second meeting, where I did the speaker's file sharing, I was unable to resize either the file sharing "box" of the speaker's "box".  The speaker appeared in a very tiny box while the file occupied almost the whole screen.  In both meetings, I had made the speaker a Co-host.  Is there a way for me to not lose resizing ability as a Host when I am sharing the presenter's files?  It seemed as though I lost a lot of zoom control capabilities in the 2nd case ... or am I missing something?  Thanks.