Strange it isn't former CEO as you wouldn't have a CEO in a flat company. Seems hypocritical to me, but maybe it isn't and I don't get the distinction.
Otherwise, what separates a subsidiary from just being another team? I assume the difference is that a subsidiary can be legally considered to be a company on its own altogether, but I'm not a lawyer. If it is though, then assuming companies need a CEO, Zappos still needs one.