Answer
$3z^3w^2(-z^2-6w^2) \text{ or }-3z^3w^2(z^2+6w^2)$
Work Step by Step
The GCF of the coefficients is $3$.
The GCF of the literal coefficients (the variables) is the one with the lowest exponent for each variable.
Thus, the GCF for the variables is $z^3w^2$.
The GCF is $3z^3w^2$.
Factor out the GCF to obtain:
$-3z^5w^2-18z^3w^4=3z^3w^2(-z^2-6w^2)$
Alternatively, $-3z^3w^2$ can be factored out to obtain:
$-3z^5w^2-18z^3w^4=-3z^3w^2(z^2+6w^2)$
