I am answering Patrik for his last posting.
Zeiss wide angles are in two different forms. They are either small and compact like my C-Y 28 2.8 or large, long and bulky like my C-Y 21 2.8.
I had the same question in the past, why is my C-Y 21 2.8 so much longer and bigger than my Minolta 20 2.8 ?
I am no expert in the field of optics, I am only speaking with my experience in photography. Lenses with many elements tends to have less colour fringes, less distortion and excellent contrast. They also have the ability to focus in short distance. One of my friend also said many of the lens elements are there for the correction of problems like colour fringes.
For ZF 35 2, you would expect it to have good performance at f2 and close focusing. I believe for large bulky lenses, it is actually good news because you should see great performance. ZM 35 2 is excellent at f 2.5 and above but poor f2. It is Zeiss weak point at large aperture if you compare with Leica. I would expect to see good performance of ZF35 2 at f2.
C-Y 25 2.8 is compact with length 56mm. It has excellent resolution and contrast at the centre but performance quickly falls as you go to the corners. It can focus down to 0.25m. ZF 25 2.8 is big and long. I would expect it to have excellent performance even at the closest focusing distance. Its large size resembles my C-Y 21 2.8 which has a length more than 90mm.
I have to thank Patrik again for the discovery of the new ZF lenses. It would mean that once the ZF are officially announced, there will be a big drop in the prices of C-Y 21 and 25. So it is now the time to sale your old gear before the official announcement.