I can't speak for the RB 90mm lens you linked to but the RZ 110/2.8 is a beautiful lens. I used an RZ professionally for years but I also used it every time I wanted to shoot any personal work, over any of my Zeiss or Leica 35mm film equipment. The image quality of a 6x7 film will always better a 35mm film. Of course digital has now overtaken 6x7 too.
Pity about RB/RZ and M6/M7-series leaf-shutter lenses. If the Mamiya MF rangefinder lenses somehow could be made to keep the shutter OPEN it would be miraculous to use them on an EOS, I think.
