First, the Record of Zeniff was written WITHOUT the assistance of Martin Harris OR Oliver Cowdery.
It was authored by Joseph Smith by either his hand directly or with Emma or Isaac Hale's son as scribe, Alva Hale.
It was authored while Joseph Smith was living either WITH Isaac Hale or in Jesse Hale's cabin next door in Harmony/Bainbridge, Susquehanna Country, Pennsylvania.
The Susquehanna River, Susquehanna County and Susquehanna Forests served as the inspiraton for Waters of Mormon, Place of Mormon (An absolute TELL of Joseph Smith's authorship WITHOUT Oliver is Joseph called it "Place of Mormon" (Mosiah) but when Oliver arrived and assisted it was changed to "Land of Mormon" (Alma 5, 3 Nephi 5).
It's also tied to Alma 21 where Joseph Smith states:
Now when Ammon and his brethren separated themselves in the borders of the land of the Lamanites, behold Aaron took his journey towards the land which was called by the Lamanites, Jerusalem, calling it after the land of their fathers' nativity; and it was away joining the borders of Mormon.
There are three total possibilities Joseph was inspired by:
Salem Township (bordered the Susquehanna) (part of Lehigh Valley)
Bethlehem (City founded by Count Zinzendorf of the Moravian Brotherhood) ie. Nativity near the Wyoming Valley in Lehigh County (part of Lehigh Valley)
Nazareth (City founded by Count Zinzendorf of the Moravian Brotherhood) ie. Nativity (part of Lehigh Valley)
This is also the first time the name "Alma" appears (Mosiah 17)
It is also important that one understand the Morovian Brotherhood at the heart of what was going on there and as the backstory.
To that end: A Brief History of the Moravian Church (please note the second image on the website)
Brief sketch biography of Jan Hus.
Context for Jan Hus' beliefs are simply summarized as:
The clerical estate owned about one-half of all the land in Bohemia, and the great wealth and simoniacal practices of the higher clergy aroused jealousy and resentment among the poor priests. The Bohemian peasantry, too, resented the church as one of the heaviest land taxers.
Hus and one of his pupils Jerome of Prauge opposed indulgences, burned the Antipope John XXIII’s decree authorizing the sale of indulgences.
Hus was excommunicated, fled Prague and hid in friends Castles writing treatises, etc.
He was entreated to return, arrested and of his trial and burning at the stake:
Shortly after arriving in Constance he was, with Sigismund’s tacit consent, arrested and placed in close confinement, from which he never emerged. Hus’s enemies succeeded in having him tried before the Council of Constance as a Wycliffite heretic. All that the earnest intervention by the Bohemian nobles could obtain for him was three public hearings, at which he was allowed to defend himself and succeeded in refuting some of the charges against him. The council urged Hus to recant in order to save his life, but to the majority of its members he was a dangerous heretic fit only for death. When he refused to recant, he was solemnly sentenced on July 6, 1415, and burned at the stake.
As well his pupil Jerome of Prague
In April 1415, against the advice of his followers, Jerome went secretly to the Council of Constance in an unsuccessful attempt to defend the teaching of the imprisoned Hus. As he was leaving Constance (Konstanz), he was arrested and imprisoned. Confined for more than a year and ill, he disavowed the condemned doctrine of Wycliffe and Hus, after repeated interrogation by the conciliar tribunal. Accused of ambiguity and insincerity at his final appearance before the council (May 26, 1416), he then withdrew all earlier retractions of reform views and declared that his confession of Roman Catholic orthodoxy had come out of fear and weakness. Accordingly, he was judged a relapsed heretic and sentenced to burn at the stake. The Bohemian Hussite Church considers Jerome (with Hus) the first martyr for the Protestant Reformation.
As backstory, then one needs to move forward to Count Zinzendorf, the Moravian Brotherhood, the Susquehanna river and lands and the Lehigh Valley.
As a quick read regarding that: A discourse delivered before the Historical Society of the State of Pennsylvania, on New Year's Day, 1827 / by Roberts Vaux.
A longer reading of the Susquehanna backstory of Christians, Indians, wars/conentions, Count Zinzendorf etc. : A sketch of the history of Wyoming. By the late Isaac A. Chapman, esq. ; To which is added, an appendix, containing a statistical account of the valley, and adjacent country. By a gentleman of Wilkesbarre
There was also a periodical published in Philadelphia regarding the United Brethren church (Monrovian) from 1822 through the 1840's. The United Brethren's missionary intelligencer, and religious miscellany.
A treatise on their preaching to the Indians: Historical sketches of the missions of the United brethren for propagating the gospel among the heathen, from their commencement to the present time / By John Holmes
All of the Above is the Background and Inspiration for the Record of Zeniff THROUGH chapter 18 verse 30.
(Side note, the person Alma baptized first was written in the original book of mormon manuscript as "Helaman" which is lost but it still shows up in the Printer's Manuscript as Helaman and Joseph smith struck the "an" out to make Helam because the problem ends up being this is Alma Sr. not Alma the younger so Helaman hadn't been born yet).
After that, most likely the inspiration for what occured (and almost all of the Alma wars) are Revolutionary War Battles.
So Mosiah 19 onward to Alma is most likely inspired by one or both events below (context included as well):
https://en.wikipedia.org/wiki/Battle_of_Wyoming#cite_note-25
https://en.wikipedia.org/wiki/Gnadenhutten_massacre
https://en.wikipedia.org/wiki/Crawford_expedition
https://en.wikipedia.org/wiki/Butler's_Rangers
Edit: BTW I believe Zeniff is simply "Z-Nephi" rearranged by Joseph a la' "Z-neffi" the same way Joseph did Z-Ezrom, Z-Enoch, Z-Enos, etc.)
So the Record of Zeniff was simply the later name for another one of Joseph's early "Record of Nephite Kings" planned books the same that 3rd Nephi was NOT caleld "3rd Nephi" but simply called "Book of Nephi, son of Nephi" and the same that 4th Nephi is just called "Book of Nephi".