function __angy_angz(p1, p2) = 
    let(
        dx = p2[0] - p1[0],
        dy = p2[1] - p1[1],
        dz = p2[2] - p1[2],
        ya = atan2(dz, sqrt(dx * dx + dy * dy)),
        za = atan2(dy, dx)
    ) [ya, za];