another which lens...16-35 f4 IS or Zeiss 21mm 2.8

sold my 17-40 so need something wider.

I know what I will get with the canon,

My question is:

1: Can I rely on auto focus confirm?

Will be used on a tripod most of the time but when I am hiking I may not have that luxury.

I have used an older Contax mount Zeiss 35 with adapter and like the color / contrast.

To state the obvious, the ZE21 is not wider than your 17-40 and 16mm is only slightly wider than 17. If wider were really the reason you sold the 17-40, you might have been better off just adding the Samyang 14 - very nice lens and also very affordable.

But, there are still reasons for either of these other two lenses even if "wider" isn't really what you get. Either lens will be much better than your 17-40 in the IQ department but from what I've seen, whether the ZE21 is better than the 16-35 f4 IS in this area is debatable. Having said that, I've owned the ZE21 several times and I soft spot for it - it would be my choice for a couple reasons.

-I personally like the rendering of the ZE21 better than the 16-35 F4 IS.
-The useable distance scale makes manual focusing an absolute breeze.
-f2.8 is great for starscapes.

Manual focus confirmation does work on the ZE21 but it's not great for action anyway. Also, for landscapes, even off the tripod you'll be more reliant on your distance scale than the focus confirmation anyway.

But, if you need IS or zoom more then none of the things above really matter. Hope I've made things at least a little less muddy for you.

I have both. The 16-35 L IS f4 is a fantastic travel lens, sharper than the faster f2.8 models regardless of IS. However, hardly any lens matches the quality and sharpness of the Zeiss 21mm ZE.
If not having AF or IS is OK for you and you don't need a zoom, then the 21mm Zeiss can't be beat.

For me, each has its place. Doing a large group shoot--the 21. On the road--the 16-35.

Like Advaitin I have both and use both regularly. The Zeiss is the "class act" when you know that 21mm is what you want. The zoom is quite remarkable for a wide zoom and is excellent for casual unplanned stuff. I primarily use the zoom on the IR bodies as the Zeiss isn't so good at that genre.

Bob