Answer
$2d(d+1)(d-1)(3d+2)$
Work Step by Step
$6d^{4}+4d^{3}-6d^{2}-4d=$
...factor out the GCF.
$=2d(3d^{3}+2d^{2}-3d-2)$
...factor by grouping.
$=2d[d^{2}(3d+2)-1(3d+2)]$
...factor again.
$=2d(d^{2}-1)(3d+2)$
...write $d^{2}-1$ as a difference of two squares.
$=2d(d+1)(d-1)(3d+2)$
