Verified answer

[(6x^4y)/(7y)]^-3 * [(216y^3)/(x^3)]^2 =

[ 7/ (6 x^4)]^3 * [(216 y^3) / (x^3)]^2 =

(343)/(216 x^12) * (216^2 y^6)/(x^6) =

(343)/(x^12) * (216 y^6)/(x^6) =

74088 y^6 / x^18