That's quite a statement. The head of a company with a privileged view of the US residential real estate sector says that the market is "unpredictable." Not the good kind of unpredictable where you can't figure out how heavy the money bags that get dropped at your door will be. No, it's the bad kind of unpredictability where you can... lose money.
Reading between the lines, I conclude that Zillow sees a major shakeout in real estate on the horizon. They've already been hit with losses and see a lot more where that came from. In an effort to get ahead of whatever is approaching, the company is making an abrupt exit from the home flipping business.
Zillow was founded in 2006, as the last US housing market bubble was furiously inflating. It has seen a complete cycle of boom/bust. If anybody knows the US residential real estate sector, it is Zillow.