With all respect to John Carmack (and it is really a lot of respect!) I'm surprised he seems unaware of pbzip2? It's a parallel implementation scales almost linearly with the amount of cores, and has been around since ~2010, so it's not yet old enough to drive, but anyone dealing with bzip2'ing large amounts of data should have discovered it long ago.

And yes, use zstandard (or xz, where the default binary in your distro is already multithreaded) where you can.