| Step | Hyp | Ref | Expression | 
						
							| 1 |  | 2zrng.e |  | 
						
							| 2 |  | 2zrngbas.r |  | 
						
							| 3 |  | 2zrngmmgm.1 |  | 
						
							| 4 | 1 2 3 | 2zrngmmgm |  | 
						
							| 5 |  | elrabi |  | 
						
							| 6 |  | elrabi |  | 
						
							| 7 |  | elrabi |  | 
						
							| 8 | 5 6 7 | 3anim123i |  | 
						
							| 9 |  | zcn |  | 
						
							| 10 |  | zcn |  | 
						
							| 11 |  | zcn |  | 
						
							| 12 | 9 10 11 | 3anim123i |  | 
						
							| 13 |  | mulass |  | 
						
							| 14 | 8 12 13 | 3syl |  | 
						
							| 15 | 14 | rgen3 |  | 
						
							| 16 | 1 2 | 2zrngbas |  | 
						
							| 17 | 3 16 | mgpbas |  | 
						
							| 18 | 1 17 | eqtr3i |  | 
						
							| 19 | 1 2 | 2zrngmul |  | 
						
							| 20 | 3 19 | mgpplusg |  | 
						
							| 21 | 18 20 | issgrp |  | 
						
							| 22 | 4 15 21 | mpbir2an |  |