I have shape files for a whole county, and have created a base map in Qgis. What I do for my projects is zoom into the area of interest then export to dxf. The same procedure was used when I used Arcgis, however I had to go into the features and create a new feature called ELEVATION and copy the z values from the county ELEV into the newly created ELEVATION. I have tried this in Qgis but I am still not getting the contours on an elevation in cad. I have read some post about entering a code into OSGeo4WShell but the problem I have with that is my contour shape file is for a whole county and is way too big to bring into cad. I also keep getting errors so What options do I have?