Lemma multiple4_2: forall u v : Z, Zodd v -> Zodd u -> v <= u -> rel_prime u v -> 1 < u -> 1 < v -> exists two : Z * Z, let (s, w) := two in (u - v = 4 * s /\ u + v = 2 * w \/ u - v = 2 * w /\ u + v = 4 * s) /\ 0 < s /\ 0 < w /\ rel_prime s w.