The word "himself" here emphasizes that Jesus alone is the reason that Jews and Gentiles can worship God as one peaceful community. Alternate translation: "he is the one who enables us to live in peace with each other" (See: [[rc://en/ta/man/jit/figs-metonymy]])
The words "his flesh," his physical body, are a metonym for his body dying. Alternate translation: "By the death of his body on the cross" or "By dying on the cross" or "By his actions as a mortal man" (See: [[rc://en/ta/man/jit/figs-metonymy]])
Paul is speaking of Jews and Gentiles being hostile to each other and unable to worship God together as if they were on different sides of a wall. Because Jesus died, Gentiles as well as Jews can now worship God. Alternate translation: "he made it possible for Jews and Gentiles not to be hostile to each other anymore" (See: [[rc://en/ta/man/jit/figs-metaphor]])