Zeus holds a council with the other gods to decide ulysses' fate. which of the gods does he send to the island to demand that ulysses be released?

It's Odysseus and not Ulysses if this is Greek mythology (hence Zeus). That Greek God is Hermes, or Mercury if in Roman mythology (hence ulysses). Use Mercury or Hermes depending if it's Roman or Greek mythology. Determine which one is which as your question mixes the mythologies up.