How is Hashem returning His hand?
Radak: This is like "Hashiv Achor Yemino Mipnei Oyev" (Eichah 2:3).
Malbim: He is refraining from acting. He pulls back His hands, and does not let His hand go out [against the enemy]. Rather, He hides them in His bosom, not to do anything. If He would take them out, the enemy would be finished automatically. Sometimes the enemy is strong, and a miracle is needed to finish it off. This requires merit of the generation; if they do not merit, Hashem will not do a miracle for them. Here, a miracle is not needed. The enemy's nature is weak. If You will take Your right hand] out of Your bosom, they will be finished off via nature! However, You hide Your hand and prevent this.
What is the meaning of "mi'Kerev Cheikcha Chale"?
Rashi: Take [Your right hand] out of Your bosom, and fight Your enemies! "Chale" is to expel, like "Kalah Garesh Yegaresh" (Shemos 11:1).
Radak #1: Eradicate the enemy from Your bosom, i.e. the Beis ha'Mikdash, Your hidden place, like a man's bosom.
Radak #2: Expel Your right hand from Your bosom, and take our vengeance. One who puts his hand in his bosom does not do an action, like a lazy man who does so and does not work. "Chale" - do not return Your hand until doing Mishpat to the Resha'im. All this is a metaphor.
Malbim: Refer to 74:11:1:2.