I always found Tazok's dialogue after a charm person, equal parts interesting and confusing. He has a very low save vs. spell, but its easy enough to get him to fail his breath weapon save via Algernon's Cloak. Once the charm takes, talk to him and he relays the following:
"I'm a member of the Blacktalons. All I know is that we've been hired by the Zhentarim to attack the iron shipments coming along the Coast Way road."
This doesn't seem to jive with the story line and what we know of Tazok and the bandits plaguing the Sword Coast. The plot to disrupt the iron trade along the Coast Way is the Iron Throne's scheme -- not the Zhentarim's. In fact, the Zhents are investigating what is going on, same as everyone else (hence Xzar and Montaron's mission). While they are certainly also an evil organization, their main goal is to counter the Iron Throne's influence in the region. Tazok works for Davaeorn, who is also employed by the Iron Throne and is not a Zhent.
Seems to be an oversight with this dialogue. Perhaps in early drafts, the Zhentarim were considered the antagonist instead of the Iron Throne (which was obviously created for the game). It might even be worth replacing the word "Zhentarim" with "Iron Throne" to make the statement accurate, but I don't know if Beamdog has the rights to make such dialogue changes.