Answer
$9w^{4} - z^{4}$
Work Step by Step
We use the formula for the difference of squares to apply to this question.
The difference of squares formula is:
$(a-b) (a+b) = a^{2} - b^{2}$
In the given formula let $3w^{2}$ represents a and $z^{2}$ represents b.
$(3w^{2}-z^{2}) (3w^{2}+z^{2}) = (3w^{2})^{2} - (z^{2})^{2}$
= $9w^{4} - z^{4}$
