Days of heavy selling in Chinese stocks have left two major indexes in the country as the worst-performing markets of Asia-Pacific.At the close of regional markets on Tuesday, the CSI 300 — which tracks the largest stocks listed in mainland China — had plunged 8.83% so far this year. Hong Kong’s Hang Seng index also suffered heavy losses, falling 7.88% in the same period.“There hasn’t been a single two-day decline (for the Hang Seng index) since the Financial Crisis that has exceeded the magnitude of the last two days,” analysts at Bespoke Investment Group wrote in a note.Other major mainland indexes such as the Shanghai composite and Shenzhen component were also in negative territory for the year, among the few major Asia-Pacific markets that lost ground year-to-date.Separately, the MSCI Emerging Markets index has also tumbled into negative territory for the year. Chinese internet giants such as Tencent, Alibaba and Meituan were among the top 5 constituents of the index, as of Jun 30.The declines come as Chinese regulators continue to step up their oversight in sectors spanning from technology to education and food-delivery. The increased scrutiny spooked investors and sent many scrambling for the exit.Hong Kong and China markets traded mixed in Wednesday morning trade, struggling to recover from the declines of the past few days.At the start of the second half, all the major Chinese indexes and the Hang Seng were in positive territory for the year. The Shenzhen component was up 4.78% while the CSI 300 index was just 0.24% higher as of end June. Hong Kong’s Hang Seng index was also up 5.86% in the same period.Timeline of eventsThe latest sell-off in Chinese stocks started after a Bloomberg report last week said Chinese regulators are planning heavy penalties for ride-hailing giant Didi that could include massive fines and a forced delisting.Following that first domino, reports also emerged late last week of a government crackdown on China’s private education sector, which sent U.S.-listed Chinese education stocks tumbling. Chinese education stocks in Hong Kong also took a beating, with New Oriental Education & Technology Group, Koolearn Technology and China Beststudy Education Group plunging more than 30% each on Monday.Next, China’s antitrust regulator ordered Tencent on the weekend to give up its exclusive music licensing rights and slapped a fine on the company for anti-competitive behavior.cnbc.com