It would be best to put your new head into daz first. Scale and position it over the gen z models head, then move the eyes nose and mouth into the rough place you need them, as sculpting in blender can mess these up. (You may need to add the genesis 2 female morphs bundle, not sure now what comes with the basic morphs)
Then set resolution to base and export the genesis 2 model.
In blender do the same, place your scaled head on top and line it up with the genesis2 model. In sculpt mode gently pull and smooth it to the shape of your new head being careful around the eyes and nose. Don't add or remove any vertices or the import won't work later. When your done select the genesis 2 head and export (selection only, don't include the other head model) and follow the guide to get it back through daz to VAM. remember to add the morph to a new untouched genesis 2 model, not the one you changed earlier. Good Luck