The prophecy in Isaiah 40-66 cannot be dated. Isaiah may have written it at the time of Assyria's invasion or at some other point late in his ministry, which ended between 701 and 686 BC.
Isaiah 40:1-31 - Comfort for God's People
Isaiah 41:1-29 - God's Help for Israel
Isaiah 42:1-9 - The LORD'S Chosen Servant
Isaiah 42:10-17 - A Song of Praise to the LORD
Isaiah 42:18-25 - Israel's Failure to See and Listen
Isaiah 43:1-13 - The Savior of Israel
Isaiah 43:14-44:5 - The LORD'S Promise of Victory