The phrase "more deep sixed" refers to something that has been discarded or destroyed in a deliberate and secretive manner. Some synonyms that could be used in its place include "buried," "disposed of," "jettisoned," "abandoned," and "eliminated." These words all imply a sense of finality and permanence, indicating that the object in question has been removed from consideration entirely. Additionally, the phrase "more deep sixed" has a somewhat informal and slangy connotation, so it might be appropriate to use synonyms that are more sophisticated or professional, depending on the context.