## Algebra 1: Common Core (15th Edition)

$9w^6-z^4$
In this problem, we use the rule that $(a-b)(a+b)= a^2-b^2$. Here, $a=3w^3$ and $b=z^2$. $(3w^3)^2$ is $9w^6$ and $(z^2 )^2$ is $z^4$. Therefore, the answer is $\boxed{9w^6-z^4}$