Answer
$\frac{6}{z}$.
Work Step by Step
The given expression is
$=\sqrt{\frac{36}{z^2}}$
Use quotient property of square roots.
$=\frac{\sqrt{36}}{\sqrt{z^2}}$
Use $36=6^2$.
$=\frac{\sqrt{6^2}}{\sqrt{z^2}}$
Simplify.
$=\frac{6}{z}$.