"...Zeiss doesn't have a know-how to make fast zoom lens (I don't mean optically, I mean autofocus-fast)..."
Zeiss does not need the know-how for AF. Nowadays you just buy/ pay a licence fee for using an already existing AF system. There are companies like Minolta etc. out there, who offer their AF know-how on the market. Which means Kyocera bought/licenced (i do not know from whom) the right for using a specific AF in the N-Lenses. But to save money, you can choose whether this is the most up-to date AF Speed and accuracy, or whether this is an AF standard of i.e. 1992.
Having said this, it is also possible that Kyocera could not buy the newest AF technology for the N-system. Maybe the big players only "sell" the older technology to protect their own top of the line models.
As far as I know, Canon does not "sell" its technology at all. Which is for them an advantage and they do not need the money anyway
So looking at the capabilities, it would not be very difficult for Zeiss to offer lenses with very fast AF. It is just a question of the price. But there are downsides of a fast AF too.
1. To be able to achieve the highest speed in AF (just looking at the lens), you have to give up on the comfort when focussing manually. It is always a compromise. Either it is a great feeling and very easy to focus manually, or to use AF. But it is impossible to have it for both 100% at the same time.
A fast AF needs very short distances (for rotating the lenses). The longer this distance is, the more time the AF needs to be at the right spot. With manual focus, you need/want the other extreme. You want to have a lens, which you have to turn a lot to focus very smooth at the desired point. Thanks to this long distances for the right spot, it is a lot more "smooth" while focusing and you turn until it pops into focus. You seldom need to go back and forth to find the right spot. With AF cameras in general, to focus manually is very difficult.
The N-system is a compromise between the AF world and the manual focus world. The act of focussing is "steep" enough, so that you can use AF comfortable and at the same time it is still very convenient to focus manually. There is no other AF system on the market, where you can focus manually this comfortable.
Nevertheless the C/Y system is still better for focussing manually. If you compare the same lens in C/Y mount and with N-mount, the distances in C/Y to focus to a certain spot is twice as long as with the N-lens. It was designed for MF and therefore it has its strenght there (same with the Leica system, Canon FD system, Minolta x-700 system etc.)
All new systems like Canon AF, Minolta AF etc. are poor if you want to use it in MF mode. No comparison with the older, pure MF systems or the newer Contax N-lenses. So this was IMO quite smart of Zeiss, to produce lenses that fullfill the wishes for both costumer groups.
2. The second point is quality control in the lens production. A lens designer will always prefer a very stable lens where you can fix easier the exact position of lenses within the tube. Preferrably no movements at all. Actually it is a contradiction if you think about it. On one hand, the designers spend huge R&D money, to achive the best optical quality for a lens (price/performance wise). You calculate the best performance with the way lenses are fixed to each other within the tube. On the other hand, with AF you need more flexibilty within the tube and not too heavy material to make it faster. I do think this is the reason why it is so difficult to produce Zeiss quality for AF lenses. With new materials, this is now better/ easier than maybe 15 years ago, but is is still not too easy or cheap.
Regarding Zeiss lenses with Canon etc. mount:
I know that Leica tried that a couple of years ago. They asked all the big names. But nobody wanted to cooperate. I think this could be done without a huge price premium on top of the normal Canon-L lenses. It is all a question of quantity and quality control. As far as I know, the quality control during the production of Zeiss lenses is pretty efficient and therefore not too expensive. And if the quantity will be 3-4 times than the Contax market, there will be no problems with the price. Look at the Sony cooperation. The Sony digital P&S are neither more expensive than Canon or Minolta P&S.
The main problem IMO is the lack of entrepreneurship in the past at Zeiss. Zeiss only produced lenses, if someone else ordered it and they could be sure they get payed for it. This is how it worked with Kyocera, Rollei, Hassy, Sony etc. They never did it at their own risk.
This seems to change now with the Zeiss Ikon system. I guess they realized, that the damage of doing nothing while Contax is going south is bigger then the risk to loose money with the Zeiss Ikon system. We talked many times about the reputational risk with Zeiss and tried to convince them to ask Kyocera for more committment.
It is not just Contax, which is a problem for Zeiss. Rollei did not order anything over the last years neither (because of prices IMO), and Hassy went to Fuji with the H1 incl. lenses.
So Zeiss has now to be more active and entrepreneurial in the photo market to support their own name and reputation. Should (if that would happen) a couple of cooperation partners are going south, Zeiss obviously does not want to go the same direction with their photo division because of bad reputation of dead partners
So they try it now with Cosina. Lets see how this will go...
Apropros Cosina. There are patents on lens mounts. The Leica M-mount was protected for decades. But you can not renew it without a significant change of the lens-mount or its technology to stay protected. This is why the Konica Hexar RF and all the other Voigtländers etc. came out suddenly. The protection was over. And this is why Zeiss can offer the Zeiss Ikon with M-mount. I do not know whether they have to pay royality fees additionally, but I doubt it.