I bought my first Zookeeper from the 1999 CA Extreme show. I didn't know enough at the time to know that it was actually a Qix cabinet with Zookeeper parts in it. That was fine with me, since I was just having fun playing, but then I saw a dedicated cabinet on eBay and had to have it. Nobody bid on it because the price was too high. The little gears in my head started turning and I figured I could pay a little extra for it and then turn around and sell my Qix-turned-Zookeeper cabinet to help pay for it. That's exactly what I did. I got the new cabinet and it was joyful.
I then sold my old cabinet to my friend, Stephen Beall. It was joyful for him, too, but only for a little while. He reported some problems that turned out to be coin processor related, so I gave him the coin processor board from my new Zookeeper. It didn't help. I told him to bring me the cabinet back and I would get it working. It was stubborn. Both cabinets developed problems and actually stopped working all together because of the stupid coin processor board. I got real pissed off. I decided to look at the MAME source code and figure out what the coin processor did and how it worked. It turns out that its only purpose in life is to prevent people from converting Qix boards to run Zookeeper by swapping ROMs. Well, that would not do at all. Stupid thing.
I brushed up on my 6809 assembly language skills and proceeded to crack the stupid protection and made it work without the coin processor board at all. I managed to do it in about three nights of crunching my eyebrows up real close to think better and the Zookeepers have both worked flawlessly ever since. (Of course, I had to put in a new PC-AT power supply and replace horrid board-eating battery with a NVRAM board designed by Mark Spaeth). You can download the patched code from my "technical info" page if you want to get rid of your coin processor too.