\(\left(-x^3.z.y\right).\left(\dfrac{2}{3}.y.x^2\right)^2\)
\(=-x^3.z.y.\dfrac{4}{9}.y^2.x^4\)
\(=-\dfrac{4}{9}x^7.y^3.z\)
`(-x^3zy)(2/3yx^2)^2`
`=-4/9x^3zy.y^2x^4`
`=-4/9x^{3+4}.y^{1+2}z`
`=-4/9x^7y^3z`
\(\left(-x^3zy\right)\left(\dfrac{2}{3}yx^2\right)^2\)
\(\Leftrightarrow\left(-x^3yz\right)\left(\dfrac{2}{3}x^2y\right)\left(\dfrac{2}{3}x^2y\right)\)
\(\Leftrightarrow-\left[x^7y^3z\left(\dfrac{2}{3}\right)^2\right]\)
\(\Leftrightarrow-\dfrac{4}{9}x^7y^3z\)