Well, I did

apt-get install unzip --allow-unauthenticated

however, if I remember right, this requires the activation of rzr' repository, witch is a bit involved. Maybe there is an easier way to find and install unzip (if this really is the solution also for other devices than mine; I don't really understand what is happening here).

Maybe the dependencies identified by your procedure include unzip?

Unfortunately, for googlemaps.jar, the issue seems to be more complicated, since the error message I receive in terminal is strange and I can't understand...