Can you unzip it outside of Thunderbird? That would be my suggestion. Then, after unzipping it, you can copy into the thunderbird profiles folder (optional) or place it anywhere. Then, in thunderbird, click help>troubleshootinginformation, scroll down to 'profiles' and click 'about:profiles', click next, then enter a short name for the profile, and then click the 'browse' button to locate and select the unzipped profile and activate it.

Can you suggest/inform an application that can unzip files above 4GB, outside of TB?