I can see that your code intends to unzip the file into a buffer, and then to open and query the contents of that buffer ... but, exactly what happened when you “tried it?”   What messages did you receive?   Do you know or can you determine whether, for instance, the bunzip2 step actually worked?   For that matter, [how] do you know that the contents of the zipped-file are, in fact, correct?   “Never assume.™”   Leave no stone face-up.

And, okay, what difference would it make if you did uncompress it into a (temporary) file?   If you unzipped it to a file, queried the file, then deleted the file?   If one variation of an approach doesn’t work, and another variation’s readily at hand which is almost the same thing, perhaps try “plan B” ...