(1)(2xy2z)(? 1 3 xy)= - 2 3 x2y3z;(2)4ab(2ab2+3a2b)=8a2b3+12a3b2; (3)(2x+y)(x-2y)=2x2-4xy+xy-2y2=2x2-3xy-2y2.故答案为- 2 3 x2y3z;8a2b3+12a3b2;2x2-3xy-2y2.