Problem:
 h(f(f(x))) -> h(f(g(f(x))))
 f(g(f(x))) -> f(f(x))

Proof:
 Unfolding Processor:
  loop length: 2
  terms:
   h(f(f(x4)))
   h(f(g(f(x4))))
  context: []
  substitution:
   x4 -> x4
  Qed