I own a 5D3 and 24 TSE MK II and Nikon mount Zeiss 21 f/2.8 F2 (that I use on a D800E and the 5D3 via adapter). The 24 TSE MK II and the Zeiss are both extraordinary lenses. Over tho, I prefer the Canon 24 TSE MK II. The image quality stopped down a bit is every bit as wonderful as the Zeiss (microcontrast included) plus you have the movements as a bonus. The 24 TSE MK II is a very large reason why I'm not going all in with Nikon. I highly recommend you consider it of the price doesn't scare you off. Upsides to the Zeiss include wildly sharp corners and the fact it's faster than the Canon as well as a bit better wide open but really, if you don't need f/2.8 or the 21mm, there's little reason to chose the Zeiss over the Canon 24 TSE MK II. Also, once you get used to having tilt-shift, it's hard not have it
As an aside, I have also owned the Canon 24 TSE MK I and it doesn't come close to either the MK II or Zeiss.
I totally agree with ak's statement. I have the same 5D3 w/ 24TSE II and Zeiss 35, 50 f1.4, 50 f2.0, 85 and 100
lenses. Zeiss are incredibly sharp, have a great deal of micro contrast and are a joy to use. Not much cheaper than the 24TSE II but still worth the $ IMO. The Zeiss 21 is probably not as sharp as the 25mm Zeiss however it depends on where you read the reviews.
My advise, rent some of these lenses first and see if you like them.