Remember first, Zander went into the Service well before (months) before Carmen, Carl, and Rico joined up. During this time he has already gone through flight school and is established as a pilot on the ship. In order to attain this position (pilot), they need to be the best and the brightest ... extremely good with math and such. When Carmen arrives on the ship, she has just made it through flight school. At this point, Zander is not her instructor, but rather her mentor. She is qualified to fly the ship as she has already passed through flight school. BUT, there is practical learning which they did in school, and now a brand new pilot needs someone to show them the ropes in the real world. It isn't that Zander has risen so fast, it's that he's qualified to pilot the ship, so is qualified to mentor Carmen in the process.