source 2007 Bernstein--Lange compute XX = X1^2 compute YY = Y1^2 compute ZZ = Z1^2 compute YYYY = YY^2 compute M = 3 XX+a ZZ^2 compute MM = M^2 compute E = 6 ((X1+YY)^2-XX-YYYY)-MM compute EE = E^2 compute T = 16 YYYY compute U = (M+E)^2-MM-EE-T compute X3 = 4 (X1 EE-4 YY U) compute Y3 = 8 Y1 (U (T-U)-E EE) compute Z3 = (Z1+E)^2-ZZ-EE