YES
Time: 0.012

Problem:
 Equations:
  
 TRS:
  pAC(x,zero()) -> x
  pAC(pAC(pAC(pAC(a(),a()),b()),b()),b()) -> pAC(pAC(pAC(a(),a()),a()),b())
  pAC(pAC(pAC(pAC(a(),a()),a()),a()),b()) -> pAC(pAC(pAC(a(),a()),b()),b())

Proof:
 AC-RPO Processor:
  precedence:
   zero > pAC > a > b
  status:
   
  problem:
   Equations:
    
   TRS:
    
  Qed