zipfile uses zlib which is C. But it's even better than that: it releases the GIL, so it gives linear speedup with multiple threads. If you need to (de)compress a bunch of files, you can do them all at once quite easily using e.g. concurrent.futures.

If you want that speedup on the command line without Python, check out pigz. It's gzip with parallelism. Easy 10-20x speedup for some jobs.