The Zaphod sector was a region of space.
In the year 2369, on stardate 46421.32, Captain Rudolph Ransom's starship had a Romulan Neutral Zone encounter with a Romulan warbird. The Federation ship evaded the sensors of this ship by descending into the atmosphere of a gas giant. It was on operating on threat level 2 conditions. The warbird disengaged its pursuit on stardate 46421.34 and Ransom's ship continued its patrol and survey. (VOY: "Equinox, Part II")