DrGargi,
A single Zoom user can only have one active meeting open at a time. If a user login attempts to start a meeting while another meeting is in progress, they will be prompted to terminate the existing meeting prior to starting the new meeting.
Many organizations have multiple users under one Zoom account. I know that some very small organizations "share" one user login among several people, but this only works when there are a limited number of meetings, and none of them conflict.
If shorter meetings are possible for some groups, a Free Zoom user can conduct a meeting up to 40 minutes. This works with some organizations -- everybody wants shorter meetings!