There are two generations of Zeiss Standard lenses (T2.1 or T2.2 lenses). The first came out in Arri Std mount and only with the following focal lenghts: 16mm (t2.4), 24mm, 32mm, 50mm and 85mm (t2.2) and 135mm (t4). The second generation appeared circa 1983 (T2.1s) and added many more focal lenghts (from 10mm to 180mm, including 12mm, 14mm, 28mm, 40mm, 100mm, etc), PL mounts and better mechanical designs. Optically, the two generations are very similar, only the T* coatings of the MKII lenses differ, so lenses of the first generation are a bit softer, less contrasty and prone to flares/veiling.
The Superspeed or High Speed lenses first appeared in the mid 70's with the T1.4 series of lenses (18-25-35-50-85mm) and originally with bayonet mounts and focus scales both in imperial and metric systems. Some people refer to these lenses as "B-Speeds" or MKI Superspeeds. Optically these are similar to the MKII/MKIII series, but are softer, less contrasty and have a 3-blade iris that's very obvious when you stop down these lenses to t2.5-2.8. The MKII came out about the same time as the Standards T2.1 in 1983, also with more robust mechanicals, a more rounds iris, longer focus rotation and better coatings. They open up to 1.3 and have PL mounts also. The MKIII series added a rare 65mm T1.3 and improved mechanics, with more accurate and bigger focus marks, only in feet OR metric, but retain exactly the same optical characteristics of the MKII series of the previous decade.
The T1.3-1.4 series of lenses are soft and milky if used wide-open (T2.1s perform better than the superspeeds at T2.1), but are very sharp and contrasty when stopped down. Many people prefer the look of T2.1s, and claim that these series of lenses aren't 100% matching, while others still use T1.3s and fill the missing focal lenghts with T2.1s, specially the 100mm, 135mm and 180mm (T3) lenses.
To me, all of these series of lenses work great with digital sensors, without the extreme sharpness of later designs, but enough contrast and detail to shoot in almost everyday situation and more "punch" than Cooke S2/S3s, Super Baltars, Kowas, etc, which really shouldn't be used at their widest stop unless for the effect.