There is no clear document states ScreenOS could perform nat66 (at least Juniper does not use the term "nat66".) However, if one could follows ScreenOS release notes carefully, it became consequences.
Where obviously, key word "nat" does the trick!set policy id 1 from "Trust" to "Untrust" \ "Any-IPv6" "Any-IPv6" "ANY" nat src permit set policy id 1