Here is some info i found on Adapters - hope it helps.
RZ Digi Back Adapters:
The current Mamiya Digi-backs are DM-22, 28, 33, 40, 56 - while the store info below lists them as DL – DM – ZD Backs.
**********************************************************************************************
212-107 / HX701 Mamiya DM to RZ Pro IID requires separate focusing screen –
This is the Adapter that is listed in the ProIID Brochure:
$1000 @ B&H
The Mamiya RZ Digital Back Adapter for the RZ67 Pro IID allows any Mamiya digital back that is compatible with the 645AFD mount to be used on the RZ Pro IID body with full functionality, while using NO additional cables.
http://www.bhphotovideo.com/c/product/502724-REG/Mamiya_212_107_RZ_Digital_Back_Adapter.html
$750 @ Adorama
Mamiya Back Adapter Plate, Allows Mounting the ZD 22 Megapixel Digital Back on the RZ67 Pro IID (HX701)
PRODUCT DETAILS
Manufactured by: Mamiya
Mfg Part No: 212107
Adorama SKU: MYDBARZ
Allows you to use the Mamiya ZD 22 Megapixel Digital Back on the RZ67 Pro IID
http://www.adorama.com/Als/ProductPage/MYDBARZ.html
***********************************************************************************************
903-542 Mamiya RZ, RZ Pro II Adapter Kit for DM22???, DM33 Student
$1500 @ Adorama
Mamiya RZ67 Pro & Pro II Adapter Kit for the APTUS II 6 - DL33 Digital Back
WHAT’S IN THE BOX
RZ67 Pro/Pro II Adapter, DL33 only (connects Aptus-II Digital back to RZ67 Pro/Pro II camera) - Matched Camera Focusing Screen (for Aptus-II 7 digital back)
PRODUCT DETAILS
Manufactured by: Mamiya
Mfg Part No: 903542
Adorama SKU: MYDL33RZ67AK
Mamiya RZ67 Pro/Pro II Adapter Kit (DL33 only)...
This adapter connects the Aptus-II Digital back to the RZ67 Pro/Pro II camera. Includes matched camera focusing screen for use with the Aptus-II 7 digital back. Cat. #903-542
http://www.adorama.com/Als/ProductPage/MYDL33RZ67AK.html
***********************************************************************************************
903-545 Mamiya RZ, RZ Pro II Adapter Kit for DM28, DM40???
$1600 @ B&H
The Mamiya 903-545 DL28 Back Adapter Kit for the RZ67 Pro & Pro II attaches to the rear of a Mamiya RZ67 Pro or RZ67 Pro II 6x7cm film camera, allowing the Aptus II DL28 digital back to interface with these cameras.
A dedicated focusing screen is also included, complete with framing outlines which precisely match the DL28's 33 x 44mm image area dimensions. You're left with better-than-100% viewfinder coverage; not only will you be able to see the image area perfectly, but because a RZ67 screen is ~66 x 66mm you'll also be seeing quite a bit of what lies beyond the image area to allow you to better time an action shot.
• Exclusive back adapter to allow DL28 digital back upon Mamiya RZ67 Pro/Pro II cameras
• Dedicated focusing screen included (with framing lines displaying the DL28's 33 x 44mm image area)
• Includes male pc cord to connect to lens' shutter, and a female pc connection upon rear of adapter
http://www.bhphotovideo.com/c/product/605094-REG/Mamiya_903_545_DL28_Back_Adapter_Kit.html
$1000 @ Adorama
Mamiya RZ67 Pro & Pro II Adapter Kit for the APTUS II 6 - DL28 Digital Back
http://www.adorama.com/Als/ProductPage/MYDL28RZ67AK.html
WHAT’S IN THE BOX
RZ67 Pro/Pro II Adapter, DL28 only (connects Aptus-II Digital back to RZ67 Pro/Pro II camera) - Matched Camera Focusing Screen (for Aptus-II 6 digital back)
PRODUCT DETAILS
Manufactured by: Mamiya
Mfg Part No: 903545
Adorama SKU: MYDL28RZ67AK
Mamiya RZ67 Pro/Pro II Adapter Kit (DL28 only)...
This adapter connects the Aptus-II Digital back to the RZ67 Pro/Pro II camera. Includes matched camera focusing screen for use with the Aptus-II 6 digital back. Cat. #903-545
***********************************************************************************************
903-551 Mamiya RZ, RZ Pro II Adapter Kit for DM56
***********************************************************************************************
Phase One Mamiya RZ67 Adapter for H/P Backs w/Hasselblad V Fitting - $1350
Mfr item: 70964
http://www.vistek.ca/store/ProPhotoDigitalBacks/166037/phase-one-adapter-plate-for-mamiya-rz.aspx
***********************************************************************************************
Threads on this subject:
http://forum.getdpi.com/forum/showthread.php?t=10914
http://forum.getdpi.com/forum/showthread.php?t=9055
http://luminous-landscape.com/forum/index.php?showtopic=43741
I can't even find any info about the adapters on the Mamiya site. Its amazing with all the technology, that this info is so convoluted.