Zscaler ZCC is an agent running on all major system versions, Windows, Mac OS X, Linux, iOS, and Android and enforcing Zscaler protection.
It captures all HTTP/HTTPS from the configured device and sends it through SSL tunnels toward Zscaler proxy nodes.
General Captive Portal considerations
Since Zscaler ZCC captures all HTTP traffic, it prevents captive portal detection from working correctly, as this detection relies on HTTP.
Running Cloudi-Fi with Zscaler with the same cloud as ZCC
ZCC is associated with a Zscaler cloud. When Cloudi-Fi is set up on the same cloud, ZCC authentication takes the leadership and prevents Cloudi-Fi authentication from kicking in.
As a result, all devices with ZCC enabled will pass through the Guest network without seeing the captive portal.