Hi Ron,
I do not know specifically about the Z220, but I'll have a go at answering your question from my experience with other strobes.
1) If you wire in the SB80 and use the Z220 on slave then it will fire with the pre-flashes and miss the actual exposure. Won't work.
2) If you wire both to the camera with 5 pins. The Z220 signal will stop the D100 from taking a picture and the camera will lock up. Which is what you have experienced.
3) If you wire the SB80DX in with 5 pins and the Z220 in with 2 or 3 pins on the other synch socket - quite a few housings will work like this - then both will fire for the main exposure. The problem is that the SB80DX does its DTTL metering on the pre-flashes - determines the flash output then and sticks with it. Then for the main exposure you are adding light from another strobe, the Z220, which in addition to the correct amount of light from the SB80DX will cause an over exposure (unless you back the light from the Z220 right back. And if you are doing this then you might as well shoot 2 manual guns.
It is very difficult to get a reliable lighting system with one SB80DX and one other strobe. I have heard people say that they have used two housed SB80DXs with success, but I have no experience of this myself.
Alex