There is a Leica 35-70mm f/4 that some people really like, but I don't know if it is better than the CZ. If you do a search you will see this has been debated here before. The almost mythical (because they made so few and because of it's supposed IQ) Leica 35-70mm f/2.8 is probably better than the CZ, but I have never even seen pictures from this lens and even if you found it it would cost a huge amount. If you are willing to go with primes the latest versions of the 35 elmarit, 50 summicron, and 90 elmarit make a great trio for landscapes that cover much the same range and you should be able to pick up all three for less than $1,000. I hope this helps.
Considering your setup I am not sure you would gain anything at all by ditching the 35-70 for anything else in that range. Your short zoom is top notch and as Steve puts it: the 2.8 Leica version is seriously expensive. I have limited experience with 35mm focal lengths but the one slr lens I had was the Distagon 35/2.8, very lightweight, very sharp and quite cheap. The Leica 35/2.8 was not in the same league. I borrowed one and tried it on my Leica R7 but it was nothing to write home about, really.
The Contax 28-85 gets mixed reviews whereas the Contax N 24-85 is liked by some.
There is a Leica R 28-90mm zoom which is supposedly the bees knees but it will cost you an arm and a leg and I was never keen on it as I prefer my limbs intact.
On the wider side I have the Leica R28/2.8 latest, which is stellar. As a slim traveling kit I bring it together with a 60mm macro lens and (wish I had something wider) make do with it.
I have both slow and fast primes through the range, but for the type of landscape shooting I often do I find zooms invaluable. I wonder with the the 5DII if I'll still find the 35-70 as good as primes when stopped down. I don't have a 1DsIII so I never shot my lenses FF at high pixel density.
I do like my Canon 24-105 f4 IS for walking around. But it must have twice the number of elements as the 35-70 and on the wide end it is not "prime like". And then there's the distortion on the wide end.....
Does anyone have an opinion if the 35-70 is optimized at the wide end or long end? The 14-24 is clearly optimized wide, and the 70-200 seems optimized long. But I'm not sure about the 35-70.
You have exactly the same set up as me. I shoot the 1DsIII and I cant honestly say you can get a better team from my ALenses knowledge (which isnt that vast).
All I can say is that after doing rigorous tests on all these lenses that I am more than happy with the partnership they provide. The weakest link for me was the wide angle and now thats sorted with the 14-24. The 35-70 is a remarkable lens on the 1DsIII and shows up the 24-105 that I own. Its a lens I now only reach for when travelling.
I think you in a great place right now for a 21mp sensor.
