Verses 9 and 11 are a word for word quote of Isaiah 11:4-5. Verse 10 is sandwiched in there to comment on "slay the wicked" before he moves on with the quote. It is not the first time Nephi does something like this.9 And with righteousness shall the the poor, and reprove with equity for the of the earth. And he shall smite the earth with the rod of his mouth; and with the breath of his lips shall he slay the wicked.10 For the speedily cometh that the Lord God shall cause a great among the people, and the wicked will he ; and he will his people, yea, even if it so be that he must the wicked by fire.11 And shall be the girdle of his loins, and faithfulness the girdle of his reins.
Now compare verse 10 with 1 Nephi 22:15-18
I have argued before that the unnamed "prophet" in the second half of 1 Nephi 22 is Zenos. In that case, Nephi is quoting or paraphrasing Zenos in 2 Nephi 30:10. The reason I find this interesting is the tremendous knowledge of the scriptures that Nephi demonstrates. He quotes Isaiah, feels for some reason that one of the verses needs more elaboration, is aware of the fact that a passage by Zenos helps clarify what Isaiah is writing, and paraphrases that before moving on with the Isaiah quote.15 For behold, saith the prophet, the time cometh speedily that Satan shall have no more power over the hearts of the children of men; for the day soon cometh that all the proud and they who do wickedly shall be as ; and the day cometh that they must be .16 For the time soon cometh that the fulness of the of God shall be poured out upon all the children of men; for he will not suffer that the wicked shall destroy the righteous.17 Wherefore, he will the by his power, even if it so be that the fulness of his wrath must come, and the righteous be preserved, even unto the destruction of their enemies by fire. Wherefore, the righteous need not fear; for thus saith the prophet, they shall be saved, even if it so be as by fire.
This is in fact very similar to what Nephi does in 1 Nephi 19:11 - 1 Nephi 22:28. Here he first quotes Zenos (19:11-19:17), then eventually he starts quoting Isaiah in chapters 20-21. In 22:1-14, Nephi comments on and keeps paraphrasing Isaiah. Then in 22:15-28, he seems to quote and paraphrase Zenos along with his own comments. This all comprises a coherent unit of text. To Nephi, Isaiah and Zenos seem to go hand in hand.
What little we have of Zenos' writings turns out to have had an influence on several Book of Mormon prophets's writings. Assuming that Zenos wrote a lot more than the few quotes we have in the Book of Mormon, I wonder how much else is influenced by him.