Can't be done. the Aperture control, sadly, on Contax 645 lenses is electronically controlled by the camera. There is no aperture ring. A lot of people wish this wasn;t so, believe me.
That said, any Mamiya, Hasselblad (F or C) or Pentax 645 lens WITH an aperture ring can be used.
edit - if you want at a Zeiss fix outside of the ZF line, Hasselblad's F/FE and C/CF/CFi lenses are Zeiss lenses (see Zeiss or Hasselblad home pages for datasheets). The C__ series of lenses for the V-mount bodies (shutter in lens) can be used via an adapter - simply cock the shutter and put in F mode. I use/used the Hassy 110/2 F, Mamiya 200/2.8 APO and Mamiya 150/3.5N on a 1Ds2 with amazing results.