source 2015 Renes--Costello--Batina "Complete addition formulas for prime order elliptic curves", Appendix A.1
parameter b3
assume b3 = 3 b
compute t0 = X1^2
compute t1 = Y1^2
compute t2 = Z1^2
compute t3 = X1 * Y1
compute t3 = t3 + t3 
compute Z3 = X1 * Z1
compute Z3 = Z3 + Z3 
compute X3 = a * Z3 
compute Y3 = b3 * t2 
compute Y3 = X3 + Y3 
compute X3 = t1 - Y3 
compute Y3 = t1 + Y3 
compute Y3 = X3 * Y3 
compute X3 = t3 * X3 
compute Z3 = b3 * Z3 
compute t2 = a * t2 
compute t3 = t0 - t2 
compute t3 = a * t3 
compute t3 = t3 + Z3 
compute Z3 = t0 + t0 
compute t0 = Z3 + t0 
compute t0 = t0 + t2 
compute t0 = t0 * t3 
compute Y3 = Y3 + t0 
compute t2 = Y1 * Z1
compute t2 = t2 + t2 
compute t0 = t2 * t3 
compute X3 = X3 - t0 
compute Z3 = t2 * t1 
compute Z3 = Z3 + Z3 
compute Z3 = Z3 + Z3