| Step | Hyp | Ref | Expression | 
						
							| 1 |  | elfz2 |  | 
						
							| 2 |  | znn0sub |  | 
						
							| 3 | 2 | adantr |  | 
						
							| 4 | 3 | biimpcd |  | 
						
							| 5 | 4 | adantr |  | 
						
							| 6 | 5 | impcom |  | 
						
							| 7 |  | zre |  | 
						
							| 8 | 7 | adantr |  | 
						
							| 9 | 8 | adantr |  | 
						
							| 10 |  | zre |  | 
						
							| 11 | 10 | adantl |  | 
						
							| 12 | 11 | adantr |  | 
						
							| 13 |  | zaddcl |  | 
						
							| 14 | 13 | adantlr |  | 
						
							| 15 | 14 | zred |  | 
						
							| 16 |  | letr |  | 
						
							| 17 | 9 12 15 16 | syl3anc |  | 
						
							| 18 |  | zre |  | 
						
							| 19 |  | addge01 |  | 
						
							| 20 | 8 18 19 | syl2an |  | 
						
							| 21 |  | elnn0z |  | 
						
							| 22 | 21 | simplbi2 |  | 
						
							| 23 | 22 | adantl |  | 
						
							| 24 | 20 23 | sylbird |  | 
						
							| 25 | 17 24 | syld |  | 
						
							| 26 | 25 | imp |  | 
						
							| 27 |  | df-3an |  | 
						
							| 28 |  | 3ancoma |  | 
						
							| 29 | 27 28 | bitr3i |  | 
						
							| 30 | 10 7 18 | 3anim123i |  | 
						
							| 31 | 29 30 | sylbi |  | 
						
							| 32 |  | lesubadd2 |  | 
						
							| 33 | 31 32 | syl |  | 
						
							| 34 | 33 | biimprcd |  | 
						
							| 35 | 34 | adantl |  | 
						
							| 36 | 35 | impcom |  | 
						
							| 37 | 6 26 36 | 3jca |  | 
						
							| 38 | 37 | exp31 |  | 
						
							| 39 | 38 | com23 |  | 
						
							| 40 | 39 | 3adant2 |  | 
						
							| 41 | 40 | imp |  | 
						
							| 42 | 41 | com12 |  | 
						
							| 43 | 1 42 | biimtrid |  | 
						
							| 44 | 43 | imp |  | 
						
							| 45 |  | elfz2nn0 |  | 
						
							| 46 | 44 45 | sylibr |  |