1. ((A & B) & C) & D,
2. (D & C) → F,
3. (B & C) → G,
4. (A & D) → H ├ H & (G & F)
5. (A & B) & C 1, Simplification
6. A & B 5, Simplification
7. A 6, Simplification
8. B & A 6, Commutation
9. B 8, Simplification
10. C & (A & B) 5, Commutation
11. C 10, Simplification
12. D & ((A & B) & C) 1, Commutation
13. D 12, Simplification
14. A & D 7,13, Conjunction
15. H 4, Modus Ponens
16. B & C 9,11, Conjunction
17. G 3,16, Modus ponens
18. D & C 13,11, Conjunction
19. F 2,15, Modus Ponens
20. G & F 17,19, Conjunction
21. H & (G & F) 15,20, Conjunction
Edwin