Answer
$(x+2y)(x-2y)$
Work Step by Step
Since the sides of the larger square are $x$ units each, the area of the larger square is $x \times x=x^{2}$ units.
Since the sides of the smaller square are $2y$ units each, the area of the smaller square is $2y \times 2y=4y^{2}$ units.
The shaded area is $=x^{2}-4y^{2}=(x)^{2}-(2y)^{2}=(x+2y)(x-2y)$
