(-z/x^2y)^-3/(xz/-y)^-2*(-x/y^2)^4
=(-x^2y/z)^3/(-y/xz)^2*(x^4/y^8)
=(-x^6y^3/z^3)/(y^2/x^2z^2)*(x^4/y^8)
=(-x^6y^3/z^3)*(x^2z^2/y^2)*(x^4/y^8)
=-x^12/zy^7
(-z/x^2y)^-3/(xz/-y)^-2*(-x/y^2)^4
=(-x^2y/z)^3/(-y/xz)^2*(x^4/y^8)
=(-x^6y^3/z^3)/(y^2/x^2z^2)*(x^4/y^8)
=(-x^6y^3/z^3)*(x^2z^2/y^2)*(x^4/y^8)
=-x^12/zy^7