The World of Warcraft API has a list of functions that you can interact with and to talk with WoW using Lua. These are your building blocks for manipulating WoW windows and chat boxes and so forth. Looking at these for the first time can be very daunting. But don't be discouraged. After getting more familiar with Lua the WoW API gets much easier, and the documentation gets much easier to read. Keep in mind there are many different ways to accomplish your goals, so when going though the API keep looking until you find a way that best suits what you need.
I also wanted to note that a lot of users, I found on the Web claimed Dugi’s Guide to be faster. However, all these users had either used Zygor Guides for very little time or had not used it at all. I have to give a point to each Dugi’s Guide and Zygor Guides as they both deliver a great lvling speed. For all you Dugi’s guide users out there who really feel that Dugi’s Guide is faster, I will give Dugi an extra point. If there really were a difference, it wouldn’t be by much.