The Achievement description Paradox gives you is pretty vague & Online sources are quite limited on this specific Achievement.
Start a New game or open a save that has Cheats disabled. Next, Map out Three separate but moderately sized Pedestrian Districts next to each other. Then, place down your DLC paths. Once you've mapped out 3 Districts, you'll zone one in Residential, One in Commercial, and one in Offices. Make sure that they are in Focus, as you require at least 150 for it to be. It's okay for different zoning to exist so long it doesn't inhibit it.
That's it. If it doesn't immediately pop up, try Waiting, Adding Connections, or Rezone.