Question 68367
-->{{{x^3y^3 - 64}}}
   {{{(xy)^3 - 4^3}}}
   {{{(xy - 4) ((xy)^2) + 4xy + 16)}}} 
Answer is :
   {{{highlight((xy - 4)(x^2y^2 + 4xy + 16))}}} 

Checking: Distributive property
    {{{((xy)((xy)^2) + 4xy + 16)-((4)((xy)^2 + 4xy + 16))}}} 
   {{{xy(xy)^2 + 4x^2y^2 + 16xy - 4x^2y^2 - 16xy - 64}}}
   {{{x^3y^3 - 64}}}