The problem with running Fate/Zero is even though its a prequel, its meant to be viewed AFTER Fate/Stay Night. Otherwise you spoil a lot of the latter.
Yeah. I don't know, I go back and forth on what's better to see first all the time. On the one hand, if you see Fate / Zero first then certain major facts get out and major villains are given away. A lot of Stay Night's twists get spoiled, there is no doubt about that. On the other though, if you experience Stay Night first, you know exactly how Zero ultimately ends.
Doesn't Fate/Zero originate from an H-game? You don't need to have played that, do you?
Nope. I understood the 2006 Fate/Stay Night anime without it. Moreover, I believe the new anime coming out this fall is doing its own thing and will likely diverge from the visual novel in many spots. Also, Zero is backstory to Stay Night (and started out as a novelization).
The problem with Fate/ZERO is that uncut the episodes generally hit the 25-26 minute mark. Even with the complete removal of the OP/ED themes and previews the show would still be too long to broadcast on American TV. Now, that's not affecting Black Lagoon for whatever reason (they're running that one uncut at 24 minutes) but they don't seem to be granting Aniplex the same mercy. If they were to run Fate/ZERO, they might as well make an entire timeslot devoted to infomercials, because they can't cut anything more out of Bleach or Shippuden to compensate.
Oh. Well. Hmm. That might be a problem. Might be possible to do some creative editing and have it work. Whether they'd think it'd be worth it to do so might be another matter though.