# go down to Egypt

The phrase "go down" is used here because Egypt is lower in Elevation than Jerusalem.

# those who go down

"those people of Judah who go down"

# lean on horses

"rely on their horses" 

# they are mighty

The word "mighty" here implies that they are mighty because there are so many of them.

# nor do they seek Yahweh

"nor do they ask Yahweh to help them"