source 2015 Bernstein--Chuengsatiansup--Kohel--Lange
parameter minustwo
assume minustwo = -2
compute R = Y1 + Z1
compute S = Y1 - Z1
compute T = R^2
compute U = S^2
compute V = T + 3 U
compute W = 3 T + U
compute C = R V
compute D = S W
compute E = 3 C - d X1 (W-V)
compute X3 = minustwo X1 D
compute Y3 = (D + E) Z1
compute Z3 = (D - E) Y1