YES

TRS:

  a__zeros() -> cons(0(),zeros())
  a__U11(tt()) -> tt()
  a__U21(tt()) -> tt()
  a__U31(tt()) -> tt()
  a__U41(tt(),V2) -> a__U42(a__isNatIList(V2))
  a__U42(tt()) -> tt()
  a__U51(tt(),V2) -> a__U52(a__isNatList(V2))
  a__U52(tt()) -> tt()
  a__U61(tt(),L,N) -> a__U62(a__isNat(N),L)
  a__U62(tt(),L) -> s(a__length(mark(L)))
  a__isNat(0()) -> tt()
  a__isNat(length(V1)) -> a__U11(a__isNatList(V1))
  a__isNat(s(V1)) -> a__U21(a__isNat(V1))
  a__isNatIList(V) -> a__U31(a__isNatList(V))
  a__isNatIList(zeros()) -> tt()
  a__isNatIList(cons(V1,V2)) -> a__U41(a__isNat(V1),V2)
  a__isNatList(nil()) -> tt()
  a__isNatList(cons(V1,V2)) -> a__U51(a__isNat(V1),V2)
  a__length(nil()) -> 0()
  a__length(cons(N,L)) -> a__U61(a__isNatList(L),L,N)
  mark(zeros()) -> a__zeros()
  mark(U11(X)) -> a__U11(mark(X))
  mark(U21(X)) -> a__U21(mark(X))
  mark(U31(X)) -> a__U31(mark(X))
  mark(U41(X1,X2)) -> a__U41(mark(X1),X2)
  mark(U42(X)) -> a__U42(mark(X))
  mark(isNatIList(X)) -> a__isNatIList(X)
  mark(U51(X1,X2)) -> a__U51(mark(X1),X2)
  mark(U52(X)) -> a__U52(mark(X))
  mark(isNatList(X)) -> a__isNatList(X)
  mark(U61(X1,X2,X3)) -> a__U61(mark(X1),X2,X3)
  mark(U62(X1,X2)) -> a__U62(mark(X1),X2)
  mark(isNat(X)) -> a__isNat(X)
  mark(length(X)) -> a__length(mark(X))
  mark(cons(X1,X2)) -> cons(mark(X1),X2)
  mark(0()) -> 0()
  mark(tt()) -> tt()
  mark(s(X)) -> s(mark(X))
  mark(nil()) -> nil()
  a__zeros() -> zeros()
  a__U11(X) -> U11(X)
  a__U21(X) -> U21(X)
  a__U31(X) -> U31(X)
  a__U41(X1,X2) -> U41(X1,X2)
  a__U42(X) -> U42(X)
  a__isNatIList(X) -> isNatIList(X)
  a__U51(X1,X2) -> U51(X1,X2)
  a__U52(X) -> U52(X)
  a__isNatList(X) -> isNatList(X)
  a__U61(X1,X2,X3) -> U61(X1,X2,X3)
  a__U62(X1,X2) -> U62(X1,X2)
  a__isNat(X) -> isNat(X)
  a__length(X) -> length(X)

max/plus interpretations on N:

  a__zeros_A = 141
  a__zeros#_A = 141
  cons_A(x1,x2) = max{113, 115 + x1, 140 + x2}
  cons#_A(x1,x2) = max{113, 115 + x1, 140 + x2}
  0_A = 0
  0#_A = 0
  zeros_A = 0
  zeros#_A = 0
  a__U11_A(x1) = max{144, 2 + x1}
  a__U11#_A(x1) = max{144, 2 + x1}
  tt_A = 105
  tt#_A = 105
  a__U21_A(x1) = max{144, 2 + x1}
  a__U21#_A(x1) = max{144, 2 + x1}
  a__U31_A(x1) = max{141, 81 + x1}
  a__U31#_A(x1) = max{141, 81 + x1}
  a__U41_A(x1,x2) = max{228, 124 + x1, 220 + x2}
  a__U41#_A(x1,x2) = max{228, 124 + x1, 220 + x2}
  a__U42_A(x1) = max{229, 88 + x1}
  a__U42#_A(x1) = max{229, 88 + x1}
  a__isNatIList_A(x1) = max{141, 131 + x1}
  a__isNatIList#_A(x1) = max{141, 131 + x1}
  a__U51_A(x1,x2) = max{114, 20 + x1, 59 + x2}
  a__U51#_A(x1,x2) = max{114, 20 + x1, 59 + x2}
  a__U52_A(x1) = max{125, 55 + x1}
  a__U52#_A(x1) = max{125, 55 + x1}
  a__isNatList_A(x1) = max{60, 3 + x1}
  a__isNatList#_A(x1) = max{60, 3 + x1}
  a__U61_A(x1,x2,x3) = max{112, 52 + x1, 139 + x2, 48 + x3}
  a__U61#_A(x1,x2,x3) = max{112, 52 + x1, 139 + x2, 48 + x3}
  a__U62_A(x1,x2) = max{157, 38 + x1, 138 + x2}
  a__U62#_A(x1,x2) = max{157, 38 + x1, 138 + x2}
  a__isNat_A(x1) = max{119, 9 + x1}
  a__isNat#_A(x1) = max{119, 9 + x1}
  s_A(x1) = max{157, 12 + x1}
  s#_A(x1) = max{157, 12 + x1}
  a__length_A(x1) = max{137, 2 + x1}
  a__length#_A(x1) = max{137, 2 + x1}
  mark_A(x1) = max{142, 123 + x1}
  mark#_A(x1) = max{142, 123 + x1}
  length_A(x1) = max{136, 2 + x1}
  length#_A(x1) = max{136, 2 + x1}
  nil_A = 106
  nil#_A = 106
  U11_A(x1) = max{143, 2 + x1}
  U11#_A(x1) = max{143, 2 + x1}
  U21_A(x1) = max{143, 2 + x1}
  U21#_A(x1) = max{143, 2 + x1}
  U31_A(x1) = max{100, 81 + x1}
  U31#_A(x1) = max{100, 81 + x1}
  U41_A(x1,x2) = max{227, 124 + x1, 104 + x2}
  U41#_A(x1,x2) = max{227, 124 + x1, 104 + x2}
  U42_A(x1) = max{143, 88 + x1}
  U42#_A(x1) = max{143, 88 + x1}
  isNatIList_A(x1) = max{19, 19 + x1}
  isNatIList#_A(x1) = max{19, 19 + x1}
  U51_A(x1,x2) = max{113, 20 + x1, 38 + x2}
  U51#_A(x1,x2) = max{113, 20 + x1, 38 + x2}
  U52_A(x1) = max{74, 55 + x1}
  U52#_A(x1) = max{74, 55 + x1}
  isNatList_A(x1) = max{0, x1}
  isNatList#_A(x1) = max{0, x1}
  U61_A(x1,x2,x3) = max{111, 52 + x1, 20 + x2, 20 + x3}
  U61#_A(x1,x2,x3) = max{111, 52 + x1, 20 + x2, 20 + x3}
  U62_A(x1,x2) = max{139, 38 + x1, 20 + x2}
  U62#_A(x1,x2) = max{139, 38 + x1, 20 + x2}
  isNat_A(x1) = max{0, x1}
  isNat#_A(x1) = max{0, x1}

precedence:

  zeros > a__zeros = nil > mark > cons = 0 = a__isNatIList > a__U41 = a__length = isNatIList > a__U61 = length = U41 > a__U62 = U61 > a__isNatList = a__isNat = s = U62 > a__U51 = isNatList = isNat > a__U52 = U51 > tt = U52 > a__U11 = a__U21 = a__U31 = a__U42 > U11 = U21 = U31 = U42