What is the completely factored form of this polynomial?
81x4¹-164
(3x²+2y²) (9x + 4y)(9x - 4y)
(9x2 + 4y2)(9x2 - 4y²)
(9x² + 4y²)(3x - 2y)²
(9x² + 4y²)(3x + 2y)(3x-2y