Rachel Margalioth lists arguments for linguistic unity of Isaiah.
Rachel Margalioth, The Indivisible Isaiah: Evidence for the Single Authorship of the Prophetic Book (Jerusalem: Sura Institute for Research; New York: Yeshiva University, 1964), 43-55
Designations of God
Apart from the usual designations of God we frequently encounter in Scripture, such as "the Lord," "the Lord God," "the Lord of hosts," "the Lord God of hosts," and the like, we may find designations and attributes for God peculiar to one prophet and not to be found in the words of other prophets. The introduction has mentioned such phrases as "the source of living waters," "the portion of Jacob," "the hope of Israel" as attributes employed only by Jeremiah. Likewise, we may point to the expression "the glory of the God of Israel" as specific to Ezekiel, "the God of heaven" used basically by Nehemiah, and similar singularities. This study presents us with a series of titles and designations which are characteristic of Isaiah alone and are repeated time and again in both sections. These designations are unique, not only in themselves, but also equivalent in usage in both sections.