You asked
Canon ef 50mm f 1 4 usm vs zeiss milvus 50mm f 1 4?
Both are 50mm f/1.4 lenses for full frame, so the real difference is focus. The Canon EF 50mm f/1.4 USM autofocuses, which makes it the easier choice for quick shooting and people. The Zeiss Milvus 50mm f/1.4 is manual focus only, so it suits slower work where you're happy turning the ring yourself.
Your camera mount decides a lot. On a Canon body, the Canon EF is the natural pick, for example with the Canon EOS 5D Mark IV. The Zeiss also fits Canon EF bodies, so it's an option there if you prefer manual focus. If you shoot Nikon, the Zeiss is your 50mm f/1.4 option, and it pairs well with the Nikon D850.
Written by Claude from this site's pages.