MAYBE
Trs:
 {   c(c(z, x, a()), a(), y) -> f(f(c(y, a(), f(c(z, y, x))))),
          f(f(c(a(), y, z))) -> b(y, b(z, z)),
  b(a(), f(b(b(z, y), a()))) -> z}
 Comment:
  We consider a duplicating trs.
  FAIL:
   Open