I'm not sure If I understand you correctly, However as a long time A1200T BVision user I can try and help you a little bit.
BVision
BVision is connected DIRECTLY off the PPC card. As far as I am aware it cannot be connected anywhere else. Then again I haven't got a Z4 so I wouldn't know, but I would assume not.
CGX 4.
Cybergraphics 4 works fine, try the latest available patch downloadable from the vgr website.
However, I must point out that as far as I know, the way Cybergraphics works, means that you cannot have the Bvision and AGA running at the same time. (no pass through?)
Install CGX4. (then install latest update) once done, you must run the CGXmode program stored in prefs.
Select and configure all the screen modes you will want to use. - Think from 8 bit screens (for games) up to 1152 x 900 in 16bit mode and up to 1056 x 768 on 24bit screens
(off course this does depend on your monitor - BE CAREFULL or you could kill your monitor!)
Please note that you will have to have a monitor plugged into the BVision card to see the screenmodes as you test them.
Once done, save changes and re-boot, you Bvision monitor driver will be updated in Devs/Monitors
For myself I find 16bit 1024 x 768 perfectly good enough.
Once you have done that, look in prefs and select your prefered resolution. That's it. AGA will close and all output will now be through the BVision.
As to the CV64 - I don't know. But I would guess the way CGX is set up, it precludes any chance of having two graphics cards running. Of course, I could be wrong and someone else may know better...
I hope this has helped you in some way.
Good luck.