Alibaba Group Holding Ltd., China’s biggest e-commerce company that held its initial public offering last year, bought $56.2 million of stock in U.S. online retailer Zulily Inc. this week, according to a regulatory filing. The purchases brought Alibaba’s holdings of Seattle-based Zulily to 11.5 million shares, or a 9.3 percent stake, according to regulatory filings and data compiled by Bloomberg. Alibaba’s Zulily holdings were worth $152.9 million at Friday’s closing price of $13.30.