A new feature of Outlook is that it turns every new meeting you create in Outlook into an online Teams meeting. However, this can be extremely confusing if you book a Zoom meeting and the result is that half of all the participants sit in Zoom, while the rest went to the Teams meeting.
At the moment it is not possible to turn off this feature centrally, but we are working with Microsoft to solve this in the future.
If you want to turn off the function manually, you can do so via:
Archive > Options > Calendar
Uncheck: Add online meeting to all meetings
Then click OK
You can also watch the following video that shows how to do it: