Gérer la vue avec partage d'écran

Bonjour @laurakra !
Je ne parle pas Français. I hope English will be fine!

There are some options to control the view like that. 
The most advanced which gives you full control of the view is to use Production Studio. It is available to hosts holding a Zoom Sessions or Zoom Events license, and can be used on regular webinars, or an event webinar. 
Here's a quick overview: https://www.youtube.com/watch?v=4U4RtJq1_NA
Just create different scenes with different speakers and/or with shared screen, and you can switch between them. 

A more basic option is to use the new "Shared content only" view mode which allows you to remove any cameras from view, and only focus on the shared content. With this basic method it is not possible to show only a speaker on video, and to get that effect the person sharing must stop and restart sharing. Which is why I recommend looking at Production Studio for more production control, still completely within the Zoom application with no extra hardware needed.