Carrara is not particularly efficient with internally saved texture maps. In fact, sometimes the internally saved shaders are twice as large as an externally saved shader including all of the texture maps. 

So, for packaging up a scene, it's usually best to simply locate the texture maps right next to your .car file and link to them - either having them in a folder or simply sitting there. This way the file path will be consistent when unzipped on a users computer. Then, you'll need to include a written description about why and where the maps should go for users.

Mark