Answer
$4k^2m^3(1+2k^2-3m)$
Work Step by Step
The GCF of the coefficients is $4$.
The GCF of the literal coefficients (the variables) is the one with the lowest exponent for each variable.
Thus, the GCF of the variables is $k^2m^3$.
The GCF is $4k^2m^3$.
Factor out the GCF to obtain:
$4k^2m^3+8k^4m^3-12k^2m^4=4k^2m^3(1+2k^2-3m)$