a: \(=3x^2y^2\left(3x-5y\right)\)
b: \(=\left(5x-7y\right)\left(5x+7y\right)\)
c: \(=xy\left(x-y\right)-7\left(x-y\right)=\left(x-y\right)\left(xy-7\right)\)
d: =(x+4)(x+5)
e: \(=\left(x-y\right)^2-9z^2=\left(x-y-3z\right)\left(x-y+3z\right)\)
f: \(=\left(x^2-1\right)\left(x^2-4\right)=\left(x-1\right)\left(x-2\right)\left(x+1\right)\left(x+2\right)\)