If I still have the email I'll link to the new body, it is no longer a body and back camera, it's all integrated and they do not list the AF or AFD anymore with the ZD back. The 645ZD did not list anything in regard to film backs or exposure counts, and the pictures showed a body that did not look like the back came off. The only thing listed with the ZD back was the RZ Pro IId.
In that email I also chastised them for not making the ZD back work with the older bodies, it would have been a pretty simple thing to do with an external cord.