1.(Z>C) • A 2. D v (C>D) 3. ~ D /~ZvP 4. D v (~C v D) 2, Material implication 5. D v (D v ~C) 4, Commutation 6. (D v D) v ~C 5, Association 7. D v ~C 6, Tautology or Idempotent 8. ~C 7, 3, Disjunctive syllogism 9. Z > C 1, Simplification 10. ~Z 9,8, Modus Tollens 11. ~Z v P 10, Addition Edwin