$$(3ab+cb)^{2}+9(cd-ab)^{2}+6(3ab-cd)(cd-ab)$$
$c\left(6ab^{2}+6abd+cb^{2}+3cd^{2}\right)$
$6abcd+6acb^{2}+3\left(cd\right)^{2}+\left(bc\right)^{2}$
