I enjoyed runnning this adventure and like the Zhentil Keep theme. I really like the lore around Zhentil Keep and brings back fond memories when I played the old 2e Ruins of Zhentil Keep. The combats are slightly weak, but most Tier 3 AL groups are overpowered at this point anyways with certain magic items they can obtain.
The NPCs have good flavor for roleplaying. The main NPCs motives are a little contrived and I would have wished for a little more specifics for one of the pivotal encounters (i.e., persuade or gett attacked). However, this does allow for the DM to use there own ability to make the encounter memorable and not be the same everytime.
The ending leaves the characters in a slight cliff hanger, so if possible I suggest running the 3 modules in this series together.
Overall enjoyed running the module and look forward in finishing out the next two!