If you are sure they are in the correct folder, did you restart DS as the content library will need to be refreshed. You can also right click on the library and click refresh.

As DS used map folders it is important they are in the correct folder and not installed in a nested fashion as in not My Daz 3DLibrary/My Daz 3DLibrary/Product.

Are these zips specific for DS if they are for Poser you will find them under Poser formats

Where did you intall them to?