Zillow has been planning on coming out with this for awhile. Although for many this may seem as "competition", I don't believe the margins on the properties they will be offering will be large enough for investors to even consider. It may definitely get in the way when it comes to beginner investors looking immediately to Zillow or Redfin for properties and property values (as they usually do), but for experienced investors I believe they will be able to see right through their deals.
I'm sure Zillow will launch a massive marketing plan for this platform, and will catch the eyes of many. I think the best approach to this situation is when dealing with (beginner) investors who are referencing properties they have seen on Zillow, show them the margins of those properties compared to properties you are have available. That should provide a quick ending to their arguments.
Thanks for bringing this up I'd love to hear some feedback from other professionals around the county!