These cards aren't listed in Engel but they were listed in Sports Card Magazine when they listed the non-BBM baseball card sets in the July issue every year (or at least every year that I was getting SCM regularly). The 2000 set had a base set of 109 cards - cards 1 to 108 plus an unnumbered checklist. There are an additional 36 cards that I'm guessing are short printed - a nine cards subset devoted to Senichi Hoshino (cards 109 to 117), a "Millennium Best 9" subset (cards 118 to 126) and another 18 card subset that I can't translate. Zippy Zappy's card is from the "Millenium Best 9" subset. The 2001 set had a base set of 90 cards - cards 1 to 88 plus two unnumbered checklists. There are 20 more cards that are short prints - I'm not sure what the subset is called but it looks like it contains 2001 Dragons players. There apparently is also one or more parallel versions of these 20 cards.
I was ultimately successful in finding some of these cards. I got two cards from each set. Surprisingly I didn't find them in Nagoya although I suspect I would have if I'd looked harder at any of the three stores I was in there. I picked them up at Wrappers in Tokyo.
Here are the 2000 cards: