Next, it's time to download the ZClient and the ZLOrigin Clients (you need both!), the pages you get from those links look the same as the ones from the link on Step 2 above, so you will click on "Continue" ("Weiter" in the original German) as usual, and the files will be automatically downloaded.
Copy the file "ZClient.exe" that you just downloaded to "C:\Program Files\ZClient" (Create the folder if you don't have it and give your operating system administrative privileges if it asks for you to do so), right click on it and "Run as Administrator". Insert your credentials in the program and click Connect. ⚠ Be always sure that you are not running the Original EA's version of Origin BEFORE each and every time you run ZClient!!! In case you have any doubt of it, open the task manager and kill any origin process(es) inside the details tab. After being authenticated, minimize (do not close) the ZClient's window (so it keeps running in the background). You can create a shortcut to ZClient into your Desktop if you'd like to do so, since you will need to run it every time you play.
Now, to install ZLOrigin you will extract the contents of the file "ZLOriginSetup.zip" that you downloaded in the Step 6 above, open the folder where you extracted it to, right click "Setup.exe" and "Run as Administrator". The program will suggest a location for you to install it, but you can customize it to any place you want, except for the folder where you might have the original EA version, if you have it on your computer (never install unlocked with original versions of the game or Origin, unless instructed otherwise).
Each time you play (or install / update a game) you will have to run the ZLClient, thenZLOrigin, which is basically an unlocked version of Origin with very similar functionality (never use your real EA credentials on them!).