Goal:
  
  z : Z
  z0 : Z
  k : t
  H : Some (Z.max z z0) = k
  H0 : (z < z0)%Z /\ Z.max z z0 = z0
  ============================
   (Some z = k \/ Some z0 = k)


DEBUG:Going to execute:
elim id
Level 2: evaluation returns
<coq-core.plugins.tauto::is_conj@0>
where
tauto_flags := 
of type
tauto_flags
X1 := (z < z0)%Z /\ Z.max z z0 = z0
of type
constr of type tacvalue