Yes it's that simple. For our purposes, .apk files are largely just renamed .zip files. Change the file extension, then extract from the file like a normal .zip file.

In some cases, renaming to .zip is all you need. In that case, you can stop here. However, it is becoming more and more common that mobile games use a proper game engine like Unity. In those cases, you will have to go back to the overview page (Step 2) and reapproach the files.