t0 = X1+Y1 B = t0^2 C = X1^2 D = Y1^2 E = a*C F = E+D H = Z1^2 t1 = 2*H J = F-t1 t2 = B-C t3 = t2-D X3 = t3*J t4 = E-D Y3 = F*t4 Z3 = F*J