When Zeniff and his original party returned to the land of Nephi, they were going back to fight the Lamanites to "destroy them" (Mosiah 9:1) This didn't happen and Zeniff returned to Zarahemla. In Mosiah 9:3 Zeniff mentions that he was "over-zealous to inherit the land of our fathers." We can probably assume from such remarks that the object of the failed original party was also to inherit the land of their fathers. Were there any other factors involved? Other than a guess that a lower elevation such as Zarahemla might have tropical heat and that a higher elevation such as Nephi might have a temperate climate, the text doesn't offer many clues. Perhaps Zeniff was of royal Nephite birth and not satisfied with the position of power allocated to him in the land of Zarahemla under the rule of Mosiah1. [Alan C. Miner, Personal Notes] [See also the commentary in Mosiah 9:5]
Geographical [Theory Map]: Mosiah 9:3-13 (Omni 1:29-30) Zeniff Returns from Zarahemla to Lehi-Nephi (Year 407)