\[(c - 4)^{2} - 3(4 - c)^{3} =\]
\[= (c - 4)^{2} + 3(c - 4)^{3} =\]
\[= (c - 4)^{2}\left( 1 + 3(c - 4) \right) =\]
\[= (c - 4)^{2}(1 + 3c - 12) =\]
\[= (c - 4)^{2}(3c - 11).\]