Issue isn't ZeroMQ. The simple/inefficient way to do it is to capture frames one at a time, and send them via ZeroMQ. Video is pretty bandwidth intensive .. the only reason things like YouTube work as smooth as they do is that they use codecs such H264/265 (which are proprietary unfortuantely) and stream compress frames over the network. Now doing the codec in software burns a lot of CPU as this is very math intensive .. most processors support hardware video codecs for this purpose. There are just no open source tools/libraries that make this good/simple enough that I have found.

Aren't IP cameras capable of H264 already encoded the video before output it to the network? H264 video stream has very good compression ratio and shouldn't consume too much bandwidth.

In the project I used zeromq, we were not using external IP cameras. My experience with IP cameras is still full of some seconds of latency .. I have no idea why.