While the main trilogy are all tactical role-playing visual novels, the ZAN games replace the tactical battle strategy with hack-and-slash brawler-style action RPG gaming.
The first ZAN game was based on Utawarerumono: Mask of Deception, the sequel to the original Utawarerumono game. Although the main characters from Mask of Deception are the same, it’s a retelling of the story of protagonist Haku and heroine Kuon. In much the same way, the second ZAN game will borrow from Utawarerumono: Mask of Truth, the third game in the main series.
According to reports, ZAN 2 will only be available in Japanese at first. There has been no word yet on an English localization. Previous games in the franchise have been localized, so that would suggest that an English version will arrive, eventually.
If you prefer manga and anime over games, there have been several adaptations of the games, although some are probably easier to find than others. Crunchyroll has Utawarerumono: The False Faces, which is based on the second game. Funimation has the 2006 version of Utawarerumono.