Al Payne only released two ZZT games, but they are very good ones.
Smiley Guy was one of the six winners of the Epic's "ZZT's Revenge" contest (along with Ezanya). Unlike those other five, Smiley Guy employs a lot of object enemies and gives the player more support through health and hint kiosks. Although the writing and dialogue may occasionally come off as rigid, the quality and level of detail put into the game itself is very heartwarming. Not to mention the setting (a "living lab") is atypical of ZZT games and well illustrated with plenty of line and object tiles, as opposed to just being a bunch of square rooms with yellow borders. It contains a lot of maze puzzles, occasionally warranting a change in program speed, but hey, it's a game. (And it's better than the usual invis-o-maze crap.) One could say that this is the first ZZT game to not play exactly like Town of ZZT.
Toxic Terminator, Smiley Guy's followup, was made the following year, and it continues the same general design (weird locations, maze puzzles, hint system) over a longer adventure. Released two years before the STK colour set was made public, Payne drew up several interesting screens that still look pretty cool to this day. My only real gripe with it is a dark maze that you're told to navigate without any torches. There were descriptive clues as you bumped into certain walls ... maybe I'm just dumb, but it didn't make any sense to me.
Besides that one gripe, Smiley Guy & Toxic Terminator are good quality, upper-tier stuff somehwhat reminiscent of various computer adventure and puzzle games from the mid-to-late 80's. There's really not much else to say about them since they speak for themselves very well. Definitely try them if you haven't before!