Here the enemy's "hand" refers to the enemy's control. Alternate translation: "He has allowed the enemy to capture the walls of her palaces" (See: [[rc://en/ta/man/translate/figs-metonymy]])
Here the word "her" may refer either to the temple or to Jersualem. Possible translations are 1) "the walls of the temple" or 2) "the walls of Jerusalem's palaces." The word "walls" is a synecdoche for the whole building, and the building is a synecdoche for all of Jerusalem. (See: [[rc://en/ta/man/translate/figs-synecdoche]])
This is an ironic comparison between the happy, noisy festivals of Israel and the loud shouts of victory of the Babylonians. Alternate translation: "They have raised a shout in the house of Yahweh, as the Israelites would during an appointed feast" (See: [[rc://en/ta/man/translate/figs-irony]])