2 z - 4*z + 8
z^2 - 4*z + 8
(x + -2 + 2*I)*(x + -2 - 2*I)
(x - 2 + 2*i)*(x - 2 - 2*i)
2 8 + z - 4*z
8 + z^2 - 4*z
8.0 + z^2 - 4.0*z
8 + z*(-4 + z)