\[4m^{2}n^{4} - 64m^{2}p^{4} =\]
\[= 4m^{2}\left( n^{4} - 16p^{4} \right) =\]
\[= 4m^{2}\left( n^{2} - 4p^{2} \right)\left( n^{2} + 4p^{2} \right) =\]