(x → y) → ((y ∧z) → (x →y)) = (¬x ∨ y) → ((y ∧z) → (x →y)) = (¬x ∨ y) → ((y ∧z) → (¬x ∨ y)) = (¬x ∨ y) → (¬(y ∧z) ∨ (¬x ∨ y)) = ¬ (¬x ∨ y) ∨ (¬(y ∧ z) ∨ (¬x ∨ y)) = (x ∧¬ y) ∨ ((¬y ∨ ¬z) ∨ (¬x ∨ y)) = (x ∧¬ y) ∨ (¬y ∨ y) ∨ ¬z ∨ ¬x = (x ∧¬ y) ∨ 1 ∨ (¬z ∨ ¬x) = 1