From publisher blurb:
The Black Hack (TBH) is a traditional tabletop roleplaying game, played with paper, pencils and dice - it uses that Original 1970s Fantasy Roleplaying Game as a base. But it adds and takes away elements to make it a distinct streamlined flavor of the original roleplaying game.
The Zero Edition (Zebra) Hack goes back to a great emulation of The Original Game, Swords & Wizardry: White Box. It adjusts the classes to White Box standards, adds the three original demi-human races, and brings the spells and monsters from the White Box edition into the mix. You should be able to run 0E/WB characters straight out of the box.