Lost Monkeys is a very old ZZT game made by Chris Jong. Those who have studied their ZZT history lessons well, probably remember that Chris was a member of the ZZT Club part 2 on Prodigy; the very first ZZT "company" (well, sort of). Chris' The Long Voyage series for SuperZZT belong to the first few ZZT/SuperZZT games not made by a real-life friend that I ever played... Lost Monkeys is, in my opinion, Chris' best game for ZZT.
In Lost Monkeys you must find the two monkeys, Adam and Daisy, of professor Dave back. They fled when the professor wanted to give them a strength injection. The genre of this game is the typical "classic action/adventure", a genre that isn't made much any more nowadays. In these games there usually isn't a really strong storyline; you simply have to visit a lot of places, find items and kill enemies along the way.
The cool thing about this game is that, even though they are pre-STK, the graphics aren't that bad. There's even some basic fading in it, and that for a game made in 1992-1993! The enemies you'll encounter are all object-enemies, and there's a nice attack-stats bar below in the screen while fighting.
Overall, this game will probably not appeal to all people. But if you like the classic type of ZZT game, then this is one you ought to have played...