Goal:
  
  A : Type
  P : A → Prop
  Q : A → Prop
  a : A
  l : list A
  a0 : A
  l' : list A
  IHl : All P l → All Q l' → #|l| = #|l'| → All2 (λ x y : A, P x ∧ Q y) l l'
  ha1 : list A
  ============================
   (All P ha1
    → a :: l = ha1
      → let H := CoreTactics.block in
        All Q (a0 :: l')
        → let H0 := CoreTactics.block in
          S #|l| = S #|l'| → All2 (λ x y : A, P x ∧ Q y) (a :: l) (a0 :: l'))


DEBUG:Going to execute:
intros p