There was a need to connect the ZoneMinder server to the IP cameras via a DVR.
This situation has arisen due to the fact that the DVR is on a different subnet and the video stream goes through the switch by port forwarding.
There are no connection problems, that is, we select the Ffmpeg stream type and, depending on the registrar, the source; in this case (you need to find out the source in the instructions for the DVR)
rtsp://loginoftheadministratoroftheregistrar:registraradminpassword@IPaddressoftheregistrar:554/Streaming/channels/101
where 101 is 10 main stream and 1 stream number.
You also need to select the correct camera resolution.
However, there is a problem in that it is not possible to connect to more than one camera.
If someone knows how you can connect more than one camera to ZoneMinder, then I kindly ask you to write a solution in the comments to the article or on the forum.