SHANGHAI, April 6 (Reuters) - Shares in Chinese cybersecurity company 360 Security Technology (601360.SS) plunged on Thursday after the firm announced that its billionaire founder Zhou Hongyi and his wife were divorcing and that he would give her a 6.25% share. Shares in 360 Security, China's largest provider of cybersecurity products, fell by as much as 7.8%, its biggest one day fall since February. The company on Tuesday issued a statement saying Zhou would give a 6.25% share to Hu Huan, which was worth about 9 billion yuan ($1.3 billion) based on 360 Security's closing price that day. Thursday marked...