I remember Zokko very clearly, being a total TV addict in the 60's and 70's. The continuity announcer first introduced it as a show for children and adults who had reading difficulties, much as Vision On was primarily designed for children with impaired hearing.
It was an innovative show at the time, and linked together some wildly varied segments, including cartoons, comedy sketches, documentary pieces, etc.
I found Zokko the pinball machine just a little bit scary, and with him in total control of the show the whole experience seemed slightly surreal! He would announce a score after each pinball was released, and each score corresponded to a particular style of programme segment, e.g. "Zokko - score 15 - Ha ha!" would introduce a comedy sketch.
The sight of a silver pinball careering around, with lots of flashing lights between every segment, was bound to get a bit old after a while, so later series changed the format. All I can remember is a huge sci-fi type computer linking everything, with lots of tubes filled with bubbling coloured liquid instead of the pinball machine, and early Moog synthesizer music as the sig tune.