I have learned to stay away from some of the clothing, especially tops, because they often run very small. If there is a known size discrepancy, it is stated in the description. Known name brands in shoes, such as Clark's, Muck Luck, etc. have worked best for me. I recently ordered an a Appleseed's top and the price was a fraction of the cost in the catalog or on the web site. I have purchased directly from Appleseed's for other items and am familiar with the product sizing so I was confident in ordering from Zulily.
I have not had any return problems. A return is usually requested before a refund is issued. I have received a refund or store credit depending on the particular policy for the item. Once, a pricey gemstone bracelet lost one of the stones the first time I wore it. I contacted Zulily. They requested a photo which I provided and asked me to return it for repair which they did in a timely manner.
I have been a Zulily customer for about 8 years.