1/4x^3y^2(-2xy^2)+(-2x^2y)(1/2xy)3x^2y^2z
=-1/2x^3y^2xy^2-3x^2yxyx^2y^2z
=-1/2x^4y^4x-3x^5y^4z
=-x^4y^4(1/2+3xz)
