⊦ # x = # z → (x + y = z + y0 ↔ x = z ∧ y = y0)
# x = # z → (x + y = z + y0 ↔ x = z ∧ y = y0), # y = # y0, x + y = z + y0 ⊦ x = z ∧ y = y0
Used terms: x, z, y, y0