| Step | Hyp | Ref | Expression | 
						
							| 1 |  | fzoval |  | 
						
							| 2 | 1 | 3ad2ant2 |  | 
						
							| 3 | 2 | raleqdv |  | 
						
							| 4 |  | peano2zm |  | 
						
							| 5 |  | fzshftral |  | 
						
							| 6 | 4 5 | syl3an2 |  | 
						
							| 7 |  | zaddcl |  | 
						
							| 8 | 7 | 3adant1 |  | 
						
							| 9 |  | fzoval |  | 
						
							| 10 | 8 9 | syl |  | 
						
							| 11 |  | zcn |  | 
						
							| 12 | 11 | adantr |  | 
						
							| 13 |  | zcn |  | 
						
							| 14 | 13 | adantl |  | 
						
							| 15 |  | 1cnd |  | 
						
							| 16 | 12 14 15 | addsubd |  | 
						
							| 17 | 16 | 3adant1 |  | 
						
							| 18 | 17 | oveq2d |  | 
						
							| 19 | 10 18 | eqtr2d |  | 
						
							| 20 | 19 | raleqdv |  | 
						
							| 21 | 3 6 20 | 3bitrd |  |