KJ, Z1 polish lok is a surface prep and pre-cleaner. It helps bond the actual polish (Z2 or Z5) to the paint. It should be used once a year or every 10 coats, whichever comes first.
Z6 (just a detailing spray) can be used any time before or after a coat, or right after a wash. Helps give back the slickness, kick up the shine, and keep the dust away. I use a lot of it, like the interior to help with the dust.
Z2 and Z5 are compatible, meaning you can use either one on top of the other. But, only 1 coat every 24h, uness you use ZFX. If you use ZFX, you can apply up to 3 coats right after each other (think 3 coats in an hour becasuse it dries quicker as well). But, only 3 coats per 24 period even with ZFX. If you wait a few days aver applying 3 coats in a row, you might notice a difference in mirroring when the polish cures.
