It shows some z-fighting, probably because the camera is very far from the model (which you cannot see because of viewing in Parallel Projection). Switching to Perspective and zooming to extents fixed it, unless you mean something else…
@Anssi is right: you have somehow moved the camera an absurd distance from the model. This is a common issue with parallel projection, because in that projection, unlike in perspective projection, the size of the image does not depend on the distance of the camera from the model.
I recommend that you start modelling in Perspective. I myself am already so used to it that parallel projection views appear very unnatural and I only use them for outputting standard plan, section and elevation views.
When you say an absurd distance away from the model I think I get where it went wrong.
My terrain comes from a CAD survey file and my model is very far from the origin with the grid the surveyor uses. When I first imported it, I tried to keep the original coordinate system so I could import the TIN and the line work at the same location. But the line work was all distorted, and I fixed the issue at the time by deleting every thing and import the Cad file back with the keep original coordinates unchecked. Maybe the camera issue comes from there at the begining. Anyway thanks for your help both, now I know what I can google and learn about, “camera in sketchup”.