How do I orient my zebra-covered humbuckers?

The short answer is - there really is no wrong way.  If you already own the pickups, I'd ask you first "where are the screws", and then I'd use the "screws out" orientation I describe HERE to define which way they go, as that may affect the sound.  If you haven't purchased them yet, then really it is up to you as this is a cosmetic thing.  Personally I prefer the look of the "black covers out" (or black covers have the screws), meaning the bridge black cover is closest to the bridge, and the neck black cover is closest to the fingerboard.  There are only four zebra covered pickups shown in "The Beauty of the Burst" book, but they all adhere to the "black covers out" aesthetic.  There seems to be a lot of disagreement about what is a "zebra" pickup vs. a "reverse zebra" and this changes between manufacturers (the difference being whether the slugs or the screws get the black cover).  Bare Knuckle Pickups I know uses for zebra black screws, and Seymour Duncan uses for zebra creme screws.  Frankly if you are mixing pickups from different manufacturers and you aren't sure what they do I'd email them so you are sure you are getting the orientation and look you want.  But this isn't one of those gear issues where someone can call you out on having it "wrong" - you can find pickups on major guitars in all four possible orientations, though most common is to have either black out our creme out.