First, there is a place to plug them into on the cameras.
The electronic cable releases work on both the RZ67 Pro II and the 645 Pro or Super models. There is no direct connection for a mechanical cable release on the 645 Pro or Super models, so an auxiliary adapter needs to be used with those cameras in order to use a mechanical cable release. I think (but am not sure) that the situation is the same for the RZ67 Pro II.
I don't know what the situation is with the RZ67 Pro II D.
Long electronic releases work much better than long mechanical releases. And radio remotes are much easier to implement with electronic cameras.