| Step | Hyp | Ref | Expression | 
						
							| 1 |  | zrinitorngc.u |  |-  ( ph -> U e. V ) | 
						
							| 2 |  | zrinitorngc.c |  |-  C = ( RngCat ` U ) | 
						
							| 3 |  | zrinitorngc.z |  |-  ( ph -> Z e. ( Ring \ NzRing ) ) | 
						
							| 4 |  | zrinitorngc.e |  |-  ( ph -> Z e. U ) | 
						
							| 5 | 1 2 3 4 | zrinitorngc |  |-  ( ph -> Z e. ( InitO ` C ) ) | 
						
							| 6 | 1 2 3 4 | zrtermorngc |  |-  ( ph -> Z e. ( TermO ` C ) ) | 
						
							| 7 |  | eqid |  |-  ( Base ` C ) = ( Base ` C ) | 
						
							| 8 |  | eqid |  |-  ( Hom ` C ) = ( Hom ` C ) | 
						
							| 9 | 2 | rngccat |  |-  ( U e. V -> C e. Cat ) | 
						
							| 10 | 1 9 | syl |  |-  ( ph -> C e. Cat ) | 
						
							| 11 | 3 | eldifad |  |-  ( ph -> Z e. Ring ) | 
						
							| 12 |  | ringrng |  |-  ( Z e. Ring -> Z e. Rng ) | 
						
							| 13 | 11 12 | syl |  |-  ( ph -> Z e. Rng ) | 
						
							| 14 | 4 13 | elind |  |-  ( ph -> Z e. ( U i^i Rng ) ) | 
						
							| 15 | 2 7 1 | rngcbas |  |-  ( ph -> ( Base ` C ) = ( U i^i Rng ) ) | 
						
							| 16 | 14 15 | eleqtrrd |  |-  ( ph -> Z e. ( Base ` C ) ) | 
						
							| 17 | 7 8 10 16 | iszeroo |  |-  ( ph -> ( Z e. ( ZeroO ` C ) <-> ( Z e. ( InitO ` C ) /\ Z e. ( TermO ` C ) ) ) ) | 
						
							| 18 | 5 6 17 | mpbir2and |  |-  ( ph -> Z e. ( ZeroO ` C ) ) |