\[\frac{m^{3} - 64n^{3}}{16n^{2} + 4mn + m^{2}} =\]
\[\frac{(m - 4n)\left( m^{2} + 4mn + 16n^{2} \right)}{m^{2} + 4mn + 16n^{2}} =\]
\[= m - 4n.\]