A sales slowdown and a weak profit forecast gave cybersecurity investors reason to worry.Zscaler (ZS -17.70%) stock collapsed in morning trading Wednesday, down by 17.8% as of 12:04 p.m. ET, even though the company crushed analysts' forecasts for its fiscal fourth quarter when it reported after the closing bell Tuesday.Analysts had expected the cybersecurity company to report adjusted earnings of $0.69 per share on sales of$567.9 million for the quarter. Instead, its profits were $0.88 per share, and sales ...