z x + z ----- + ----- x - z z
z/(x - z) + (x + z)/z
2 x --------- z*(x - z)
x^2/(z*(x - z))
2 x ---------- 2 - z + x*z
x^2/(-z^2 + x*z)
2 z + (x + z)*(x - z) -------------------- z*(x - z)
(z^2 + (x + z)*(x - z))/(z*(x - z))