YES(?,O(n^2))
TRS:
 {
           a__zeros() -> cons(0(), zeros()),
           a__zeros() -> zeros(),
    mark cons(X1, X2) -> cons(mark X1, X2),
             mark 0() -> 0(),
         mark zeros() -> a__zeros(),
          mark tail X -> a__tail mark X,
            a__tail X -> tail X,
  a__tail cons(X, XS) -> mark XS
 }
 DUP: We consider a non-duplicating system.
  Trs:
   {
             a__zeros() -> cons(0(), zeros()),
             a__zeros() -> zeros(),
      mark cons(X1, X2) -> cons(mark X1, X2),
               mark 0() -> 0(),
           mark zeros() -> a__zeros(),
            mark tail X -> a__tail mark X,
              a__tail X -> tail X,
    a__tail cons(X, XS) -> mark XS
   }
  Matrix Interpretation:
   Interpretation class: triangular
          [X1]    [1 3][X1]   [0]
   [tail]([X0]) = [0 1][X0] + [3]
   
             [X1]    [1 3][X1]   [1]
   [a__tail]([X0]) = [0 1][X0] + [3]
   
          [X1]    [1 3][X1]   [1]
   [mark]([X0]) = [0 1][X0] + [1]
   
                [3]
   [a__zeros] = [2]
   
             [1]
   [zeros] = [1]
   
         [0]
   [0] = [0]
   
          [X3]  [X1]    [1 0][X3]   [1 0][X1]   [1]
   [cons]([X2], [X0]) = [0 1][X2] + [0 1][X0] + [1]
   
   
   Qed