In your opinion? And what is your opinion of …I don't subscribe to the two Isaiah's theory. The evidence weighs heavily against such a theory, IMO.
The book identifies itself as the words of the 8th century BCE prophet Isaiah ben Amoz, but there is ample evidence that much of it was composed during the Babylonian captivity and later. The scholarly consensus which held sway through most of the 20th century saw three separate collections of oracles: Proto-Isaiah (chapters 1–39), containing the words of Isaiah; Deutero-Isaiah (chapters 40–55), the work of an anonymous 6th-century author writing during the Exile; and Trito-Isaiah (chapters 56–66), composed after the return from exile. While one part of the consensus still holds – virtually no-one maintains that the entire book, or even most of it, was written by one person – this perception of Isaiah as made up of three rather distinct sections underwent a radical challenge in the last quarter of the 20th century. A great deal of current research concentrates on the book's essential unity, with Isaiah 1–33 projecting judgement and restoration for Judah, Jerusalem and the nations, and chapters 34–66 presupposing that judgement has already taken place and restoration is at hand. It can thus be read as an extended meditation on the destiny of Jerusalem into and after the Exile. [wik]
… and what it the credibility of your opinion?