In this passage there have been a number of difficulties with the spelling of the names. First, Zenos is misspelled as Zenas in the 1830 edition. This misspelling is clearly a typo since elsewhere in the earliest textual sources (in both manuscripts and in the 1830 edition), Zenos is the spelling. In fact, eight out of the 12 occurrences of this name are extant in the original manuscript.
The spelling Zenock is a mistake for the correct Zenoch; for discussion of this case, see under 1 Nephi 19:10. Here in Helaman 8:20, Oliver Cowdery intended to write the name in 𝓟 as Zenock,
which was a mistake. But his final k looked almost like an h, with the result that the 1830 compositor set Zenoch, which just happens to be the correct spelling. Ultimately, however, the incorrect Zenock (the spelling elsewhere in the text) was returned to this passage (in the 1840 edition and in the second printing of the 1852 LDS edition, with reference to the 1840 edition).
The third case of spelling variation in this passage involves Ezaias versus Ezias. The printer’s manuscript reads Ezaias, but the 1830 edition, set from the printer’s manuscript, dropped out the first a, giving Ezias. It does not look like this change is due to conscious editing.
Orson Pratt, in his editing for the 1879 LDS edition, added a footnote for the name Ezias in which he proposed that this name is the same as Esaias: “Ezias may have been identical with Esaias who lived contemporary with Abraham”. Pratt then refers the reader to a passage in the Doctrine and Covenants that gives the priesthood lineage from Moses back to Esaias:
The 1906 LDS edition of the Book of Mormon made the name Ezias closer to Esaias by changing the z to s, substituting Esias for Ezias and making the corresponding change in the footnote: “Esias may have been identical with Esaias who lived contemporary with Abraham”. Yet the 1906 edition did not change the Book of Mormon name to Esaias. Obviously, the original Ezaias here in Helaman 8:20 is closer to Esaias, but is still not identical.
All three of the variant names, Ezaias, Ezias, and Esias, are unique to the Book of Mormon text. And none of these occur in the King James Bible. The closest name in the King James Bible is Esaias, the New Testament form of the name Isaiah. To be sure, we would not want to say that Ezaias, the earliest reading for the name in Helaman 8:20, is an error for the name Isaiah since the text includes both prophets in its list and thus distinguishes between the two (“and also Ezaias and also Isaiah and Jeremiah”). Moreover, since Helaman 8:19–20 lists Ezaias as one of the prophets “since the days of Abraham”, we should probably not identify him as the Esaias mentioned as the contemporary of Abraham in section 84 of the Doctrine and Covenants.
One could argue that the spelling Ezaias in 𝓟 was accidentally influenced by the immediately following Isaiah. Of course, there is no manuscript evidence for the 1830 spelling, Ezias (or for the 1906 spelling, Esias). Moreover, the name Ezaias has a z, not an s. The best solution here in Helaman 8:20 is to follow the spelling of the earliest textual source, namely the reading in 𝓟, Ezaias. This spelling is the one found in the current RLDS text (since 1908).
Summary: Restore the spelling Ezaias in Helaman 8:20, the reading of the earliest textual source (here the printer’s manuscript); as already discussed, the spelling Zenoch will be restored; in addition, the spelling Zenos will be maintained.