\[\left( x^{4} - y^{4} \right)\left( x^{4} + y^{4} \right)\left( x^{8} + y^{8} \right) =\]
\[= \left( x^{8} - y^{8} \right)\left( x^{8} + y^{8} \right) =\]
\[= x^{16} - y^{16}\]