Yes, it is fine to mix certain things. Really you just don't want to mix similiar acting products, like mancozeb and captan, trib and immunox or abound and sovran.
So I mix mancozeb, trib, and sevin.
mancozeb, immunox, sevin
captan, trib, sevin
captan, immunox sevin
abound, sevin
sovran, sevin...