en_tn_condensed/isa/40/27.md

Why do you say, Jacob, and declare, Israel ... vindication"?

The question emphasizes that they should not say what they say. Alternate translation: "'You should not say, O people of Israel ... vindication'." (See: rc://en/ta/man/translate/figs-rquestion)

Why do you say, Jacob, and declare, Israel

These two phrases both refer to the people of Israel. Alternate translation: "Why do you say, O people of Israel" (See: rc://en/ta/man/translate/figs-doublet)

My way is hidden from Yahweh

Yahweh not knowing what happens to them is spoken of as if Yahweh could not see the road upon which they travel. Alternate translation: "Yahweh does not know what happens to me" (See: rc://en/ta/man/translate/figs-metaphor)

my God is not concerned about my vindication

Possible meanings are 1) "my God is not concerned about others treating me unjustly" or 2) "my God is not concerned about treating me justly."