I used the Z1 as prep, which is fine on my car, yellow, no deep scratches, and then several coats of Z2 over time. I've heard that if you have deep scratches you should go with some Z5, but I thought you were always supposed to finish with Z2 for the best shine. Their website
www.zainobros.com explains it all. It is rather cumbersome to order from them, no online ordering system you have to print stuff out and fax it to them. If you are going to get some let me know, I have a couple of local people interested and maybe we could do a group buy...