I couldn't find specific information about which languages are included in Zone GG20 of the classification directly from the search results. The Guthrie classification, which divides the Narrow Bantu languages into geographic zones, is a possible context for your question. However, the list or specifics of the languages within Zone GG20 are not immediately available.
For precise information, you might consider consulting resources related to Bantu language classifications, such as the Bantu New Updated Guthrie List, which might provide detailed classifications and explicit entries for various zones.