To cancel your For Sale by Owner listing, first make sure you're logged into your Zillow profile. Then navigate to your listing and select "Owner View." From the owner view, please locate the "More" drop down along the blue menu bar and select "Cancel Listing."
On the following page, you'll see the option to enter "Sold" or "No Longer For Sale." If your home has sold, you an enter an optional sale price and date. Make sure to select "Update Status" and you're all set.