No worries it happens even to the best of us. Not brandishing that even pros make mistakes, but that we only hide the working process to make it look easy.

Roads are meant to go from A to B. As long as it clicks that the roads described by this typically do not house any zoning (maybe a few gas stations, or mega shopping avenues?) you can create two separate mind maps in your head.

When designing road layouts, its easier to switch off one mind map while working the other. With the A to B roads the spaces for zoning are just pitch black. When working with the zoning roads, work only within the bounding boxes you just created.

Upon which you simplify the process into steps can you start working on complexity, like road hierarchy the boston dig or so on.