-inductive ZEq: Zah \to Zah \to Prop :=
- | zeq: \forall m1,m2,m3,m4,n.
- (m1 + m4 == n) \to (m3 + m2 == n) \to
- ZEq \langle m1, m2 \rangle \langle m3, m4 \rangle
+inductive ZEq: Zah → Zah → Prop :=
+ | zeq: ∀m1,m2,m3,m4,n. m1 ⊕ m4 ≍ n → m3 ⊕ m2 ≍ n →
+ ZEq 〈m1,m2〉 〈m3, m4〉