I think it acts best as a detterent to long, strung-out wars. Obviously in a short, decisive war like HRE's it only means they put a bit higher priority on that city, but could you imagine if Slaze had built it? That being said, there are already significant deterrents agaisnt long wars as they will only just drag both civs down, so the SoZ is probably only a secondary consideration in those cases.
Edit: wow, typed this up and 5 people posted before me. Slaze athlete would be an example.
Edit: wow, typed this up and 5 people posted before me. Slaze athlete would be an example.