(3p-pq^3)2pq=
I got:
6p^2q - 2p^2q4
Can it be simplified more?
it hasn't been simplified at all. You did, however, correctly apply the distributive property to remove the parentheses.
Many people consider factoring out common values to be simplification. In that case, I'd have to say that factoring out another p, giving
2p^2q(3-q^3)
looks simpler to me.