en_tn/zec/10/11.md

will pass through the sea of their affliction

Scripture often refers to the sea as an image of many troubles and hardships. (See: rc://en/ta/man/translate/figs-metaphor)

and will dry up all the depths of the Nile

AT: "I will the Nile River to lose all its water"

The majesty of Assyria will be brought down

Here "the majesty of Assyria" probably refers to the Assyrian army. AT: "I will destroy Assyria's proud army." (See: rc://en/ta/man/translate/figs-metonymy)

and the scepter of Egypt will go away from the Egyptians.

AT: "and the power of Egypt to rule other nations will end." (See: rc://en/ta/man/translate/figs-metonymy)

This is Yahweh's declaration

This phrase is often translated as “Yahweh says” in the UDB. You can translate this concept whichever way is best in your language. This phrase is used many times in Zechariah.