Termination of the given GTRS could be disproven:

(0) Obligation:

Generalized rewrite system (where rules with free variables on rhs are allowed):
The TRS R consists of the following rules:

and(tt) → X
length(cons(N)) → s(length(L))
zeros → cons(0)
length(nil) → 0

(1) CritRuleProof (EQUIVALENT transformation)

The rule and(tt) → X contains free variables in its right-hand side. Hence the TRS is not-terminating.

(2) FALSE