Getting Started Guide - a good place to start if you are new to ZAP
Desktop User Guide - the help included with the ZAP desktop application
ZAP Developer Guide - ZAP documentation for developers
Contributing Guide - lots more details on how you can get involved
FAQ - Frequently Asked Questions
ZAPping the OWASP Top 10 (2021) - a guide mapping Top 10 items to ZAP functionality that can assist IT security personnel
Automate - the various options for automating ZAP
Authenticate - everything you need to know about authentication in ZAP
Docker - detailed information on ZAP's Docker images
Burp to ZAP Feature Map - a mapping from Burp Suite features to their ZAP equivalents
Statistics - public ZAP usage statistics
Alert Details - detailed information on the alerts ZAP can raise
Internal Events - detailed information on the internal events ZAP publishes
Internal Statistics - detailed information on the internal statistics ZAP maintains
Test Scans - the results of running ZAP vs well known deliberately vulnerable apps