Answer
$2(3z+2)(3z-2)$
Work Step by Step
Factoring the $GCF=
2
,$ the given $\text{
expression,
}$ $
18z^2-8
,$ is equivalent to
\begin{align*}
2(9z^2-4)
\end{align*}
Using the factoring of the difference of $2$ squares which is given by $a^2-b^2=(a+b)(a-b),$ the $\text{
expression
}$ above is equivalent to
\begin{align*}
&
2[(3z)^2-(2)^2]
\\&=
2[(3z+2)(3z-2)]
\\&=
2(3z+2)(3z-2)
\end{align*}