By default, ZK's logger depends on how the Web server is configured. However, you could configure ZK to load and monitor i3-log.conf as described in the Logger section of the Beyond ZK chapter.

<log>
    <log-base>org.zkoss</log-base>    
</log>

If you want to use the same logging mechanism in your application, you could configure ZK to handle all loggers as follows.

<log>
    <log-base></log-base>    
</log>

where an empty string means all packages, not just org.zkoss in the previous example.