We recently acquired specifications for all DSLR lenses by Carl Zeiss and almost always the Canon EF-mount version is larger and heavier than the Nikon F-mount version. The difference ranges from small (20g / 1mm) to large (120g / 8mm) or up to 20% difference by weight and 12% by dimension.
Is there a technical reason why there should be a difference in size? Both always cover the same full-frame imaging circle and have the same optical design, number of elements, etc. Would image quality be affected by such differences?