\(\left(4^2-25\right)^2-9\left(4x^2-9\right)^2\\ =\left(4-5\right)^2\left(4+5\right)^2-9\left(4x^2-9\right)^2\\ =9^{^2}-9\left(4x^2-9\right)^2\\ =9\left[9-\left(4x^2-9\right)^2\right]\\ =9\left[\left(3-4x^2+9\right)\left(3+4x^2-9\right)\right]\\ =9\left(-4x^2+12\right)\left(4x^2-6\right)\)