By Kirk O’Neil A Covid-19 lockdown in Zhengzhou, China, has forced the tech giant’s manufacturing plant to shut down. As electric vehicle maker Tesla (TSLA) – Get Tesla Inc Report is preparing to resume operations at its Gigafactory Shanghai after shutting down since March 28 for a Covid-19 lockdown, tech giant Apple (AAPL) – Get Apple Inc. Report faces a new threat of a manufacturing shutdown in China for one of its popular products. Tesla plans to resume production at its Shanghai plant on April 18 after a three-week shutdown that was required as part of the city’s Covid-19 lockdown. China’s…