This is what I do and did.
Now I use Zaino ZPC then Z5 ( 2 coats) then 2 coats of Z2 pro then Z8. I find that ZPC really cleans and Z5 takes out or hides imperfections then Z2 pro to perfection followed by Z8. You need Z8 and Z6 IMO.
This is what I found, to me if you not going to use ZPC then I like #80. Instead of washing after #80
I wiped my car Z6 then applied Z5 thenZ2 pro then Z8 with no bonding issues.
I also tried 39003 didn't like it, tried FP II a little better, #80 seemed to work best for me.
I also feel that Z5 is very underated, It has always worked extremely great for me. I don't detail too many other cars than my own anymore. My car needed minor care not 30 hours of buffing with 4 kinds of different products( which some cars need ) thats why I love Z5 . Z5 may not work for really bad paint ,but mine needed just that little extra not a rotory beating. I would never be without Z6 &Z8.
1.ZPC
2.#80
3. FPII
4. 3M