By 1735, misrule and extortion proved too much and the local people rose to fight. Some of them were desperate enough as to kill their wives and children before joining the rebellion, thus burning all bridges behind them. The uprising started in Taigong, then covering the area of Liping and Duyun. Local Qing administration, unable to cope with the rebels, suggested making a kind of agreement with them, but the Qianlong Emperor recalled the previous commanders and appointed Zhang Guangsi, an experienced officer under Ortai, to quell the rebellion. The uprising was bloodily suppressed, the last rebels doggedly fighting at Niupidajing. Altogether Qing armies destroyed approximately 1200 Miao forts and killed over 18,000 warriors. The campaign lasted from February to November 1736. Zhang, meanwhile appointed Governor-General of Guizhou, started to build roads, strengthening the garrisons and opening the mines, to enhance both imperial control and the economy of the region. The suppression of the revolt granted the area half a century of peace, but the deep causes of unrest remained unchanged and the tensions grew again, until Miaos rebelled anew in 1795.
Question: What was another thing Zhang did to enhance the economy?
Answer: opening the mines