To believe that early zoom lens designs of the sixties had and optical quality comparable to todays is ridiculous  This ignores the progress on optical design of the past few decades Early zoom designs typically consisted of three lens groups convergentdivergentconvergent the d group was fixed and the st and rd groups were mobile  Furthermore the st and rd group were rigidly linked so that a complex and difficult to manufacture nonlinear cambased group distance regulation mechanism wasnt needed  The downside of the rigid linking was that such a design can limit optical aberrations only over a very limited focal length range The development of sophisticated complex nonlinearly driven fourgroup based designs focusing variator compensator relay master is a fairly recent phenomenon that has been enabled by the development of new optical design techniques computation algorithms manufacturing  eg lower cost aspherical lenses numerical control machines to manufacture precise nonlinear driving cams  and material science  eg glasses with anomalous dispersion characteristics