We are given with
(x² + xy)² - (xy + y²)²
which is a difference of two square with factors of:
[(x² + xy) + (xy + y²)][(x² + xy) - (xy + y²)]
Simplifying:
(x² + xy + xy + y²)(x² + xy - xy - y²)
(x² + 2xy + y²)(x² - y²)
Which can be further factored into:
(x + y)²(x + y)(x - y)
or in simplest form:
(x + y)³(x - y)
