Why did Zhang quit Xinbang Pharmaceutical?

I am getting old. Zhang is the managing partner of Venture Capital in Xinbang Pharmaceutical. The actual controller Zhang "decided to quit because of his age and no suitable successor". Mr. Zhang, senior pharmaceutical engineer, MBA from China Europe Business School, is currently the vice chairman of Guizhou Provincial Federation of Industry and Commerce, a member of the 10th and 11th Guizhou Provincial Political Consultative Conference, and honorary dean of Health College of Guizhou Medical University. Well-known angel investors have invested in many overseas projects.