What do PAC files on the ZIA Admin Portal return based on the input?

PAC (Proxy Auto-Configuration) files are used to direct web traffic through proxies by evaluating the web requests' details and returning appropriate directives. In the context of the Zscaler Internet Access (ZIA) Admin Portal, PAC files specifically return directives indicating how a web request should be processed.

When properly configured, a PAC file can return either "DIRECT" or "PROXY." "DIRECT" indicates that a request should be processed directly without going through a proxy, while "PROXY" specifies that the request should be sent through the designated proxy server. This allows for dynamic handling of web traffic based on user-defined rules within the PAC file, effectively determining the routing of requests.

Options suggesting keywords like AUTHENTICATE, DENY, ALLOW, or BLOCK pertain to access control mechanisms rather than the function of PAC files. "ENABLE" and "DISABLE" relate more to operational settings rather than the routing instructions that PAC files provide. The crucial aspect of PAC files lies in their ability to instruct clients on whether to connect directly to a resource or through a proxy, making the correct answer clear in this scenario.