** Cloud security firm Zscaler's ZS.O shares rise 1.7% to $234.25 premarket

** Mizuho upgrades rating to "outperform" from "neutral"

** Brokerage confident that ZS is well-positioned in Secure Access Service Edge and Zero Trust markets

** Average rating of 48 analysts is "buy"; median PT is $330.45 - data compiled by LSEG

** As of last close, stock up 27.7% this year

(Reporting by Anhata Rooprai in Bengaluru)

((Anhata.Rooprai@thomsonreuters.com))