en_tn/lev/20/16.md

lies with it

This is a polite way of speaking of sexual relations. You may have to use other words in your translation. Alternate translation: "has sexual relations with it" (See: rc://en/ta/man/jit/figs-euphemism)

you must kill the woman and the animal. They must certainly be put to death

Both clauses mean the same thing. They emphasize that the woman and animal must die. (See: rc://en/ta/man/jit/figs-parallelism)

They must certainly be put to death

This can be stated in active form. Alternate translation: "You must certainly put them to death" (See: rc://en/ta/man/jit/figs-activepassive)

Their blood is upon them

The word "blood" here is a metonym for the guilt of putting someone to a violent death. See how you translated similar words in Leviticus 19:9. Alternate translation: "the guilt for their violent death is theirs alone" (See: rc://en/ta/man/jit/figs-metonymy)