Answer
$\frac{1}{z^{15}x^{15}}$
Work Step by Step
We know that $a^{−n}=\frac{1}{a^{n}}$ and $\frac{1}{a^{-n}}=a^{n}$ (as long as a is a nonzero real number and n is an integer).
Therefore, $(z^{5}x^{5})^{-3}=(z^{5})^{-3}(x^{5})^{-3}=z^{5\times-3}\times x^{5\times-3}=z^{-15}x^{-15}=\frac{1}{z^{15}x^{15}}$.