http://thomaslauer.com/comp/Lua_Short_Reference
Assuming you download the file to the Zeus install directory, you can add this to Zeus as a tool using the following details:
Cheers JussiProgram Type: DOS Command
Menu Text: Lua Reference Guide
Arguments: "c:\Program Files\Zeus\luarefv51.pdf"
Run Hidden: Selected
Capture Standard Output: Off
Capture Standard Error: Off