What are "Tzirim va'Chavalim"?
Rashi: They are expressions of birth-pangs of a woman who bends to give birth. The Tzirim (hinges) of the doors of her womb break to be opened.
Malbim: Tzirim are when the fetus begins to open the doors of the womb. Chavalim are [the pains] that continue while she sits on the birthing stone.
Who will hold whom?
Radak: (a) Birth-pangs will seize Bnei Bavel. This is like "Chil Achaz Yoshevei Pelashes" (Shemos 15:14), "ha'Lo Chavalim Yochezuch" (Yirmeyah 13:21). (b) When birth-pangs constantly seize a person, it is as if he holds them; they do not depart from him. According to Targum Yonasan, the Nun at the end of Yochezun is a pronoun, like Yochezum (will hold them). This is correct.
What is "Yechilun"?
Rashi: Chil and Chalchalah are expressions of trembling.
Why will they be astounded?
Rashi: The army against them are different [than normal troops].
Radak: The evil came suddenly; they are astounded how it occurred.
Malbim: When sudden panic comes on the Rabim, their fear increases when they see that also those around them fear and melt.
What are "Lehavim"?
Rashi #1: Their faces are beaming and terrifying.
Rashi #2: They are a nation that thinks thoughts; Bnei Bavel are compared to them due to their astonishment.
Radak: This is like one who is ashamed; his face reddens.
Malbim: They will not need to express their fear. It will be seen on their faces, which will resemble Lehavos (flames). Also, flames increase when one adds flammables to the fire; so each face will be scorched by [seeing the dread] in his colleague's face.