I know you can mix prazi and copper. I would suggest not mixing any meds unless you have to. Run CP first, then run with prazi. Reason being if a reaction occurs between them, at a minimum you could end up with a bacterial bloom that sucks the oxygen from the water.... at worst you could end up with a toxic combination that kills everything.
Mixing Prazipro with CP is a really bad idea. The Oxybispropanol found in Prazipro will often cause a bacterial bloom if mixed with CP. You can, however, mix powder praziquantel with CP.