Here "Jacob" and "men of Israel" mean the same thing. Alternate translation: "you people of Israel who are like worms" (See: [[rc://en/ta/man/translate/figs-doublet]])
Possible meanings are 1) that this refers to the opinions of other nations regarding the people of Israel or 2) that this refers to Israel's own opinion of themselves. Yahweh speaks of their insignificance as if they were a worm. (See: [[rc://en/ta/man/translate/figs-metaphor]])
Yahweh speaks of himself by name to express the certainty of what he is declaring. Translate as in [Isaiah 30:1](../30/01.md). Alternate translation: "this is what Yahweh has declared" or "this is what I, Yahweh, have declared" (See: [[rc://en/ta/man/translate/figs-123person]])