The two sons of Helaman follow in the footsteps of the four sons of Mosiah, their great-grandfather. They go preaching, eventually preaching to Lamanites. Mormon is telling this story with far fewer details than he did for the sons of Mosiah. Perhaps he had no choice. The sons of Mosiah kept personal records, and those were collected in Alma’s personal record, which was kept in the Nephite archive. Perhaps Nephi and Lehi did not keep such a record. We do not know. We do know only that Mormon tells us that they were successful among both the apostate Nephites and the Lamanites who had come into the land of Zarahemla. More than that, Mormon does not write.