The Zune debuted on November 14, so June 30th is approximately 230 days from the first sale date. At a million units, this comes out to about 4300 sales per day. Assuming that Zunes sell around the clock, that's approximately 180 Zunes per hour sold, or roughly 3 Zunes per minute.
Assuming a steady 3 Zune per minute sales rate, it will take over twenty days to sell as many Zunes as Apple currently sells iPods in a single day. And that's not even taking the current holiday-spurred iPod rush into account, which itself may be upwards of 15 million units, or about a half-million iPods per day.
We did the math, so you don't have to.