Do I need a paint cleanser like Pinnacle's before applying Zaino? I'm gonna use all of my 3M products with the polisher first, and then the Zaino. Would it be necessary to use PPCL w/ Zaino, and when do I apply it (before zaino, or before 3M)?
You should be fine without it. The only thing I would say you would need it for is if there are still some minor swirls or something. If you clay the car and polish it then you shouldn't really need any other cleaners. Swirl reducers perhaps, but cleaners no.
Pinnacle Paint Cleaning Lotion is designed for a top coat of Pinnacle waxes. They are most definitely Carnauba based. Not needed, and may make the Zaino less durable.
You don't need it. I would suggest a Dawn wash after you are finished using the 3M products. This will get rid of any residue that they may leave behind.