I have some experience with ZCS on paint. First, there is a learning curve to using ZCS. I have used ZCS on paint with no streaking. It takes practice and trial and error.
I'm sure Sal's recommendation is valid. I wasn't aware that Zaino recommended a 24 hour cure time for ZCS prior to Z8.
I have applied Z8 immediately following application of ZCS. I had good results. Now that I know the manufacturer's recommendations, I will probably follow them.
If you're wanting to do some mobile detailing using these two products, I would do a little test panel on your own vehicles (say a fender or hood) and just see how it comes out! Do one side of the hood and follow with Z8 immediately, do the other side and follow with Z8 the next day.:up