Answer
$\frac{1}{z^{2}}$
Work Step by Step
We are given the expression $\frac{z}{z^{3}}$.
To simplify, we can use the quotient rule, which holds that $\frac{a^{m}}{a^{n}}=a^{m-n}$ (where a is a nonzero real number, and m and n are integers).
$\frac{z}{z^{3}}=z^{1-3}=z^{-2}$
To simplify this into a positive exponent, we know that $a^{-n}=\frac{1}{a^{n}}$ (where a is a nonzero real number and n is a positive integer).
Therefore, $z^{-2}=\frac{1}{z^{2}}$