I listed my home I on craigs list and Zillow before listing it with a local agent. I got several views on the listing but not a single phone call. After my agent put it on the MLS many people came from out of the area to look at the property. My feeling is people found out about the property on Zillow and then called a local agent. It's hard to tell since I never got feedback from the buyers agents.
One thing you should know is that most people just click on ads and links without any intention or sometimes they just click because the ad looks good. In your case, the people who had viewed your property craigslist and zillow were probably still making decissions when you decided to use the agent and they ended up calling the agent.
The thing I really liked about Zillow is they updated information after I listed the house. They put in contact information for my agent. They were up to date on my asking price. They even included the literature from the mls.
Multiple Listing Service (MLS)
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