See link for DNS logging via Zscaler and below for actual logging taking place (for reference):
\{ "sourcetype" : "zscalernss-dns", "event" :\{"datetime":"%s{time}","user":"%s{elogin}","department":"%s{edepartment}","location":"%s{elocation}","reqaction":"%s{reqaction}","resaction":"%s{resaction}","reqrulelabel":"%s{reqrulelabel}","resrulelabel":"%s{resrulelabel}","dns_reqtype":"%s{reqtype}","dns_req":"%s{req}","dns_resp":"%s{res}","srv_dport":"%d{sport}","durationms":"%d{durationms}","clt_sip":"%s{cip}","srv_dip":"%s{sip}","category":"%s{domcat}","deviceowner":"%s{deviceowner}","devicehostname":"%s{devicehostname}"\}\}