$=8^{\frac{2}{3}}(x^{4})^{\frac{2}{3}}(y^{\frac{2}{3}})^{\frac{2}{3}}$
$8^{\frac{2}{3}}=4$$=4(x^{4})^{\frac{2}{3}}(y^{\frac{2}{3}})^{\frac{2}{3}}$
Simplify $(x^{4})^{\frac{2}{3}}:{\quad}x^{\frac{8}{3}}$$=4x^{\frac{8}{3}}(y^{\frac{2}{3}})^{\frac{2}{3}}$
Simplify $(y^{\frac{2}{3}})^{\frac{2}{3}}:{\quad}y^{\frac{4}{9}}$$=4x^{\frac{8}{3}}y^{\frac{4}{9}}$