Ensure each of your buildings and variations has a low-res and high-res version, and that they are optimized in ZBrush. Then bring everything into Blender, apply your materials wherever needed, and have everything organized and prepared for the next stage of the project. 
 

Create an initial blockout for the terrain surrounding your environment. You don't need to place any buildings or other structures in this stage, or even create much detail on the terrain itself. This stage is meant for planning the look and feel of your environment.
 

It's now time to take all the assets, buildings and structures you've created and place them within your environment. Try to use mostly your low-res models until you know where the camera will be positioned. 
 

Now that you've populated your environment, it's time to set up your camera angles. Look for interesting camera placements that emphasize the unique qualities of your environment, and don't be afraid to change architecture, lighting and other effects to fit each scene. Like Pablo showed, you can save each camera angle as its own project to ensure that it won't affect the other scenes. 
 

Render out each of your camera angles, along with any of the various accompanying render passes you think will be necessary in the paintover stage later. You can do either a fully polished set of renders, or a group of quick and dirty screenshots—whichever best suits the needs of your project (or computer).