Answer
$\frac{11z^{2}}{14}$
Work Step by Step
To write the fraction in its simplest form, find the greatest common factor of the numerator and denominator.
$ \frac{165z^{3}}{210z}= \frac{15z (11z^{2}) }{15z (14)}$
Cancel out the greatest common factor
$\frac{15z (11z^{2}) }{15z (14)}= \frac{11z^{2}}{14}$