MAYBE
Input TRS:
      1: c(a(a(x1))) -> a(c(x1))
      2: a(c(b(x1))) -> a(d(b(x1)))
      3: a(d(x1)) -> d(a(a(a(x1))))
      4: b(d(x1)) -> b(c(x1))
Number of strict rules: 4
Direct POLO(bPol) ... failed.
Uncurrying ... failed.
Dependency Pairs:
     #1: #a(c(b(x1))) -> #a(d(b(x1)))
     #2: #a(d(x1)) -> #a(a(a(x1)))
     #3: #a(d(x1)) -> #a(a(x1))
     #4: #a(d(x1)) -> #a(x1)
     #5: #c(a(a(x1))) -> #a(c(x1))
     #6: #c(a(a(x1))) -> #c(x1)
     #7: #b(d(x1)) -> #b(c(x1))
     #8: #b(d(x1)) -> #c(x1)
Number of SCCs: 3, DPs: 6
  SCC { #7 }
POLO(Sum)... POLO(max)... QLPOS... POLO(mSum)... QWPOpS(mSum)... Mat2b... failed.
Finding a loop...  failed.