// use that instead of the generic one.
	if specific, ok := matchesSpecificCurve(curve); ok {
		return specific.Add(x1, y1, x2, y2)
	}
	panicIfNotOnCurve(curve, x1, y1)
	panicIfNotOnCurve(curve, x2, y2)

	z1 := zForAffine(x1, y1)
	z2 := zForAffine(x2, y2)
	return curve.affineFromJacobian(curve.addJacobian(x1, y1, z1, x2, y2, z2))
}