\(a.3x-3y+6xy-6y^2=3\left(x-y\right)+6y\left(x-y\right)=3\left(x-y\right)\left(2y+1\right)\) \(b.4x^2-8xy-4z^2+4y^2=\left(2x-2y\right)^2-4z^2=\left(2x-2y-2z\right)\left(2x-2y+2z\right)=4\left(x-y-z\right)\left(x-y+z\right)\) \(c.125a^3-8=\left(5a-2\right)\left(25a^2+10a+4\right)\)
\(d.x^2-y^2-x-y=\left(x-y\right)\left(x+y\right)-\left(x+y\right)=\left(x+y\right)\left(x-y-1\right)\) \(e.a^2b+ab^2a^3+b^3=b\left(a^2+a^4b+b^2\right)\)