He put on. Figure of speech Anthropopatheia. Note that all the armour is for defense.
breastplate. a coat of mail.
of vengeance for clothing. of avenging for clothing. Compare Isaiah 61:2; Isaiah 63:4. The Oxf. Gesenius explains it as "of Jehovah as champion of Israel" (p. 528 b).
zeal. jealousy.