For unzipping the multipart dataset MGO12 you can either use the 7z command
7z x MGO12_freemovement_long_session.zip
Or, the unzip command, but since it doesn't support multipart files, you will need create an intermediary file with zip like this:
zip -F MGO12_freemovement_long_session.zip --out MGO12.zip
unzip MGO12.zip