Apart from the types (Planar, Distagon ect.) there are also different generations. C lenses were the first. Early ones were silvery, only the latest of these had the T* multicoating. Most had a simpler double layer coating. Silver T*s are rather rare. From the early 70s on, C lenses were black and came with T*. At the beginning of the 80s, the CF lenses were introduced to replace the C lenses. Around 2000, Zeiss introduced the CFi and CFe lenses to replace CF lenses.
Apart from these, there were also the F-lenses for use with the focal-plane series only. F-lenses were introduced in the 70s, in the early 90s electronic contacts were added so they became FE lenses.
Though the barrels changed, most lens designes stayed the same since their introduction. The 250/5,6 Sonnar is essentially still the same lens as it was in 1957. The F and FE lenses never changed in lens design, apart from some very minor modifications Zeiss did to the 110/2 in 1999. Neither did the 60/3,5, 100/3,5, 150/4 and 180/4. Concerning the 80/2,8, only very early ones were a little different. The 38/4,5 only changed when Hasselblad introduced the 905swc because of some changes in the glass formula Zeiss had to use.
The only lenses that saw considerable development were the 50/4 and 40/4. Floating elements were added in the 80s to improve close up performance of these. The 40/4 saw two major redesigns, one in 1982, when it lost a lot of weight and size, and one in 2006, when performance was improved even further.