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2*CA^2*sP34*((2 - 2*z3)/(sP4^2*z3) + ((-1 + 2*z3)*(s34 - s34*z34 + sP3*z4))/
   (s34*sP3*sP4*(-1 + z3)*z3) - (2*s34*z3^2 + sP3*(z3^2 + z4 - z4^2))/
   (s34*sP3^2*(-1 + z4)*z4))
