Exhibit 24

                                  POWER OF ATTORNEY

        The undersigned, as a Section 16 reporting person of Zscaler, Inc. (the
"Company"), hereby constitutes and appoints Remo Canessa, Robert Schlossman and
Torrie Nute, and each of them, as the undersigned's true and lawful attorney-in-
fact to:

        1.   prepare, execute in the undersigned's name and on the undersigned's
             behalf, and submit to the Securities and Exchange Commission (the
             "SEC") a Form ID, including amendments thereto, and any other
             documents necessary or appropriate to obtain EDGAR codes and
             passwords enabling the undersigned to make electronic filings with
             the SEC of reports required by Section 16(a) of the Securities
             Exchange Act of 1934 or any rule or regulation of the SEC;

        2.   complete and execute Forms 3, 4 and 5 and other forms and all
             amendments thereto as such attorney-in-fact shall in his discretion
             determine to be required or advisable pursuant to Section 16 of the
             Securities Exchange Act of 1934 (as amended) and the rules and
             regulations promulgated thereunder, or any successor laws and
             regulations, as a consequence of the undersigned's ownership,
             acquisition or disposition of securities of the Company; and

        3.   do all acts necessary in order to file such forms with the SEC, any
             securities exchange or national association, the Company and such
             other person or agency as the attorneys-in-fact shall deem
             appropriate.

        The undersigned hereby ratifies and confirms all that said attorneys-in-
fact and agents shall do or cause to be done by virtue hereof.  The undersigned
acknowledges that the foregoing attorneys-in-fact, in serving in such capacity
at the request of the undersigned, are not assuming, nor is the Company
assuming, any of the undersigned's responsibilities to comply with Section 16 of
the Securities Exchange Act of 1934 (as amended).

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to the
Company and the foregoing attorneys-in-fact.

        IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to
be executed as of this 15th day of February, 2018.


                                        Signature: /s/ Karen Blasing
                                                   -----------------------------

                                        Print Name: Karen Blasing
                                                    ----------------------------