The cybersecurity stock couldn't maintain its expensive valuation as growth slowed. Shares of Zscaler (ZS -3.66%) slid 13.3% in the first six months of the year, according to data provided by S&P Global Market Intelligence. The cybersecurity stock struggled as investors came to terms with the company's slowing growth rate and increased competition. Zscaler's last two quarters were generally favorable, but investors seem to be rethinking its valuation as the cybersecurity industry evolves. The cybersecurity ...