\[\left( - \frac{9x^{5}y^{2}}{7z^{4}} \right)^{3}\ :\left( - \frac{9x^{4}y^{10}}{7z^{3}} \right)^{4} =\]
\[= - \frac{9^{3}x^{15}y^{6} \cdot 7^{4}z^{12}}{7^{3}z^{12} \cdot 9^{4}x^{16}y^{40}} = - \frac{7}{9xy^{34}}\]