The presence of the Assyrian in verse 25 suggests that we have an instance where the later editor who inserted Babylon missed a reference. With a hundred years separating the two invasions, those at the time would not have conflated them, although from our much later perspective it is easier to see them with their similarities and presume a closeness in time.
This is the final part of the prophecy. It is the reversal of the invader who is finally destroyed. The rule of the foreigner is reversed with the elevation of Jehovah as the rightful ruler. Where Assyria, and Babylon, might have dominated earthly nations, Jehovah will dominate and rule the whole earth.
In the last days, what Jehovah wills shall be done. The image of Jehovah with his hand stretched out is a demonstration of power and dominance over the entire world.