Ich könnte jetzt auf Deutsch antwortent,
because I don't speak French, but that would help nobody.
From Google translate it seems that you want to visualize the entrance with a camera, but you don't say which kind of a camera.
With a Raspberry camera you can use "raspistill -t 0" or "raspivid -t 0" and you will see preview on HDMI monitor connected to Pi Zero.
If you want something to happen automatically on activity at entrance, software like "motion" can do that for you.
--> Raspberry camera / gstreamer / raspivid / raspiraw (bookmark list):
https://github.com/Hermann-SW/fork-raspiraw https://github.com/Hermann-SW/userland https://twitter.com/HermannSW