ZnT is a well produced and generally well written series, with an interesting idea for a plot that borrows elements from real day politics, science fiction and Nolan films sense of doom and escalation (specially The Dark Knight). However, it needed time for character development, mood setting, and time for the story to proper develop and the secrets to be revealed. If they had the budget for 26 episodes, this would have been absolutely genius. However, the characters have so much to do and so little time, they rush to the conclusions and the character arcs feel sloppy (like Five being a thrown away villain, Twelve's relationship with Lisa, her own personal life details, the detective's relationship with his daughter, and the whole school setting, which is inexplicably introduced and abandoned after one scene). Some questions are left unanswered or vague (do the children experiments make them live only a couple of decades?). The soundtrack is competent, but far from Yoko Kanno's best days. The animation is mostly top notch and those familiar with Tokyo will recognize the city's landscape, streets, buildings and atmosphere (down to every inch of detail), with a few cell shaded CG being a bit distracting.
All in all, a good attempt, but a wasted one. One can only dream of a 26 episode epic saga this series could have been.