$${ x }^{ 3 } -9 { y }^{ 3 } + { \left(x+y \right) }^{ 3 }$$
$-\left(y-x\right)\left(2x^{2}+5xy+8y^{2}\right)$
$2x^{3}+3xy^{2}-8y^{3}+3yx^{2}$
