theorem zip01 (l: nat): $ zip 0 l = 0 $;
    
      
        | Step | Hyp | Ref | Expression | 
        
          | 1 | 
           | 
          leneq0 | 
          len (zip 0 l) = 0 <-> zip 0 l = 0  | 
        
        
          | 2 | 
           | 
          eqtr | 
          len (zip 0 l) = min (len 0) (len l) -> min (len 0) (len l) = 0 -> len (zip 0 l) = 0  | 
        
        
          | 3 | 
           | 
          ziplen | 
          len (zip 0 l) = min (len 0) (len l)  | 
        
        
          | 4 | 
          2, 3 | 
          ax_mp | 
          min (len 0) (len l) = 0 -> len (zip 0 l) = 0  | 
        
        
          | 5 | 
           | 
          eqtr | 
          min (len 0) (len l) = min 0 (len l) -> min 0 (len l) = 0 -> min (len 0) (len l) = 0  | 
        
        
          | 6 | 
           | 
          mineq1 | 
          len 0 = 0 -> min (len 0) (len l) = min 0 (len l)  | 
        
        
          | 7 | 
           | 
          len0 | 
          len 0 = 0  | 
        
        
          | 8 | 
          6, 7 | 
          ax_mp | 
          min (len 0) (len l) = min 0 (len l)  | 
        
        
          | 9 | 
          5, 8 | 
          ax_mp | 
          min 0 (len l) = 0 -> min (len 0) (len l) = 0  | 
        
        
          | 10 | 
           | 
          eqmin1 | 
          0 <= len l -> min 0 (len l) = 0  | 
        
        
          | 11 | 
           | 
          le01 | 
          0 <= len l  | 
        
        
          | 12 | 
          10, 11 | 
          ax_mp | 
          min 0 (len l) = 0  | 
        
        
          | 13 | 
          9, 12 | 
          ax_mp | 
          min (len 0) (len l) = 0  | 
        
        
          | 14 | 
          4, 13 | 
          ax_mp | 
          len (zip 0 l) = 0  | 
        
        
          | 15 | 
          1, 14 | 
          mpbi | 
          zip 0 l = 0  | 
        
      
    
    Axiom use
    axs_prop_calc
     (ax_1,
      ax_2,
      ax_3,
      ax_mp,
      itru),
    
axs_pred_calc
     (ax_gen,
      ax_4,
      ax_5,
      ax_6,
      ax_7,
      ax_10,
      ax_11,
      ax_12),
    
axs_set
     (elab,
      ax_8),
    
axs_the
     (theid,
      the0),
    
axs_peano
     (peano1,
      peano2,
      peano5,
      addeq,
      muleq,
      add0,
      addS,
      mul0,
      mulS)