As I was building terrain using meshparts of the same mesh, I noticed that moving the camera farther away would cause Z-Fighting to occur, even with the same color and properties.
Z-fighting will occur with any parts that overlap at large distances. Even if you have 2 bricks that are 20 studs thick, at several thousand studs out Z-fighting will occur.
Your best option is to either prevent as much overlap as you can with the meshes, or just make sure the Z-fighting is non-existent at the viewing ranges players will use in your game.