Adafruit CSI or DSI Cable Extender for Raspberry Pi t lets you connect two 15-pin 1.0mm pitch cables end-to-end and extend the length.
It does all the pin rearranging so all you do is just snap those two cables in. Carefully pry the two ears of the connectors, plug the cables with contacts pointing up, and then push the ears back in for a solid connection.
In theory, the CSI/DSI interface isn't meant for super long cables, and you're not supposed to extend them. We connected two 1 meter long extension cables and our Display and Camera worked! But it's really not guaranteed: CSI/DSI are meant for maybe 25cm max length.
For use with classic 15-pin 1.0mm pitch flex cables, does not fit the Pi Zero's skinny CSI connector.