(* Created with the Wolfram Language for Students - Personal Use Only : www.wolfram.com *)
-(sP34*(2*CF*s34*(sP4*(-1 + z4) + sP3*z4)^2 + 
    CA*sP3*sP4*(sP4 - sP4*z4 + (sP3 - 2*s34*(-1 + z4))*z4)))/
 (2*s34*sP3^2*sP4^2*(-1 + z34)^2)
