Zillow has a new CEO, who happens to also be the old one. The real estate media company, as it calls itself, announced the change as it delivered mixed earnings for the fourth quarter last Thursday. Co-founder — and original CEO — Richard Barton will take over for Spencer Rascoff, who’s been at the helm since 2010. Under Rascoff, Zillow has grown from a $30 million real estate listing platform with 200 employees, to a $1 billion-plus company with more than 4,000 workers. Along the way, Zillow has snapped up 15 real estate and technology companies. So why the shakeup? The answer lies in Zillow’s ambitions to grow its home-flipping business.