\[(a - b)(a + b)\left( a^{2} + b^{2} \right)\left( a^{4} + b^{4} \right)\left( a^{8} + b^{8} \right) =\]
\[= \left( a^{2} - b^{2} \right)\left( a^{2} + b^{2} \right)\left( a^{4} + b^{4} \right)\left( a^{8} + b^{8} \right) =\]
\[= \left( a^{4} - b^{4} \right)\left( a^{4} + b^{4} \right)\left( a^{8} + b^{8} \right) =\]
\[= \left( a^{8} - b^{8} \right)\left( a^{8} + b^{8} \right) =\]
\[= a^{16} - b^{16}.\ \]