Pouring contempt on princes is a metaphor for causing people to feel contempt for them. Alternate translation: "He causes people to greatly disrespect those who rule" (See: [[rc://en/ta/man/jit/figs-metaphor]])
The belt is a symbol of strength. Unfastening a strong person's belt represents taking away his strength and making him weak. Alternate translation: "makes the strong people weak" (See: [[rc://en/ta/man/jit/figs-metaphor]])