| Step | Hyp | Ref | Expression | 
						
							| 1 |  | zaddablx.g |  | 
						
							| 2 |  | zex |  | 
						
							| 3 |  | addex |  | 
						
							| 4 |  | zaddcl |  | 
						
							| 5 |  | zcn |  | 
						
							| 6 |  | zcn |  | 
						
							| 7 |  | zcn |  | 
						
							| 8 |  | addass |  | 
						
							| 9 | 5 6 7 8 | syl3an |  | 
						
							| 10 |  | 0z |  | 
						
							| 11 | 5 | addlidd |  | 
						
							| 12 |  | znegcl |  | 
						
							| 13 |  | zcn |  | 
						
							| 14 |  | addcom |  | 
						
							| 15 | 5 13 14 | syl2an |  | 
						
							| 16 | 12 15 | mpdan |  | 
						
							| 17 | 5 | negidd |  | 
						
							| 18 | 16 17 | eqtr3d |  | 
						
							| 19 | 2 3 1 4 9 10 11 12 18 | isgrpix |  | 
						
							| 20 | 2 3 1 | grpbasex |  | 
						
							| 21 | 2 3 1 | grpplusgx |  | 
						
							| 22 |  | addcom |  | 
						
							| 23 | 5 6 22 | syl2an |  | 
						
							| 24 | 19 20 21 23 | isabli |  |