Unfortunately, that's the current limitation of the MS Team app. Please refer to this article as well:
https://support.microsoft.com/en-us/office/zoom-in-and-out-of-teams-dc3cd3d8-efb5-4995-8b31-434b3943ba52
You can also use MS Team online https://teams.microsoft.com please go to your computer then open your chrome or edge browser as recommended browsers. Then resize the web page by pressing Ctrl + key or Ctrl - Key to resize the web page interface and see how
it goes.
Having said that, I wanna add additional tips. To have a bigger view, please make sure you ask the participant to pin your shared screen on their end:
https://myteamsday.com/2019/10/01/teams-meeting...
You can use the Spotlight feature in a Teams meeting to put the focus on a specific person for all participants, in this case only meeting presenters can spotlight a participant. This is different from “Pin participant”, which allows an individual to pin a
video feed for their own view but not for the view of all meeting participants.
Please refer to this article on how to spotlight in MS Team:
https://support.microsoft.com/en-us/office/spot...
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Kind Regards