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