Here the word "we" refers to the Jews. This can be stated in active form. Alternate translation: "Hear, our God, for our enemies despise us" (See: [[rc://en/ta/man/jit/figs-activepassive]])
The phrase "their taunts" refers to Sanballat's and Tobiah's insults. Here the word "heads" refers to the whole people. Alternate translation: "Turn their taunts onto themselves" or "Cause their insulting words to mock themselves" (See: [[rc://en/ta/man/jit/figs-synecdoche]])