*Problem solved !

so I just tried to edit the gamelist.xml for the Lynx system (just used the regular notepad from windows). i deleted all the sections that i didnt want for 1 specific game (got rid of .7z, .lnx, LNX, ZIP) and just kept the .zip section that matches the extension type i decided to use for that specific system. It worked perfect ! now this game appeared only once in my collection. Thanks a lot for all your advises, i learnt a bit more with the gamelist files thanks to this issue.
Happy gaming