....I know how well lenses like the 1,4/85 Planar from Cosina perform - but that's the technical standard Carl Zeiss reached decades ago and was first brought to Kyocera....
Not all lenses have a direct lineage from the Contax RTS (Zeiss/Yashica) through the Contax-N (Zeiss/Kyocera) to the Zeiss ZF/ZS/ZK/ZE (Zeiss/Cosina). I will use your 84/1.4 as an example.
The original 85/1.4 CY lens began in 1975 made in West Germany. In 1990, production of that lens eventually went to Japan, up until the demise of the Contax line. Along the way, there were subtle changes such as coating changes, iris blade changes, etc. Some CY lenses underwent lens formula changes, but there is no documentation that the 85/1.4 was one of them. All in all, the 85/1.4 CY stayed pretty much the same.
The 85/1.4-N lens, an all electronic auto focus lens, bears little resemblance to its CY cousin. That lens was designed from the ground up to be an entirely new design for the N-series.
The 85/1.4 Z series was designed with Cosina's manufacturing capabilities and a competitive price point in mind, but all in all, a new design while having some roots from the original 85/1.4 CY design.
....When somebody would order a 1,4/85 or MF 2,8/80 from Carl Zeiss and would be willing to pay for their highest design/manufacturing standards in Oberkochen/Jena, you would get a - visibly - different performance....
The Carl Zeiss lenses we know today have not been made in Jena since the end of WWII. What remained in Jena was but a mere shell of the original Carl Zeiss, and after WWII became V.E.B Carl Zeiss Jena, a 'peoples owned corporation' behind the iron curtain. They had their own line of optical products.
....and now Sony/Cosina....
There has been no data or charts posted that I have seen on the Sony lenses. Anyone have any to post? From what I have read, Sony manufactures them, and Zeiss is a minor player there, providing some design guidance.
Posted below are the three Zeiss 85/1.4's (all at same scale)