\(=\left[2\left(xy+4\right)-4\left(x+y\right)\right]\left[2\left(xy+4\right)+4\left(x+y\right)\right]=\left(2xy+8-4x-4y\right)\left(2xy+8+4y+4x\right)\\ =4\left(xy+4-2x-2y\right)\left(xy+4+2x+2y\right)\\ =4\left[x\left(y-2\right)-2\left(y-2\right)\right]\left[x\left(y+2\right)+2\left(y+2\right)\right]\\ =4\left(y-2\right)\left(y+2\right)\left(x-2\right)\left(x+2\right)\)