These verses discuss later opposition to Jewish rebuilding efforts. They actually relate to events during the reign of:
Xerxes in 486 to 465 BC
Artaxerxes I in 465 to 424 BC
However, they are included here because they match the theme of opposition. Chronologically, Ezra 4:6 fits between chapters 6 and 7, while 4:7–23 fits before Nehemiah 1.