Awesome! Thanks for that. Was somewhat concerned that some of my fast MF-only glass would become unusable like it is on the 7D, but it looks like it will be ok on the 1Dx based on your link.
...Also, it would be a pity for fast Zeiss glass to be essentially unusable at max aperture.
Glad to help. Further, the specs page actually states, "Focusing Screen: Interchangeable" So, definitely ok.
I love my Zeiss lenses...I have about 40 of them! But...they're objectives for the microscopes in my labs, and it's a pity that none will mount on my dSLRs, much less focus...