No one uses Special Zebstrika ._. the only special move to even consider running is volt switch for momentum. Zeb gets killed by prio, is outsped by a ton of the metagame, and is weak as heck. Sure it gets flame charge, but it's weak as heck. And its walled by so much, any dragon, celebi, jirachi, etc. Its in the trash pit of NU for a reason.
Woah woah waoh, time out.
First of all, everyone uses special Zebstrika. It's literally the only set worth using. I'm not sure where you're getting that its only good special attack is Volt Switch when it gets excellent coverage between Electric STAB, Overheat, and HP Grass. Physical Zebstrika is completely terrible, especially seeing as how your best coverage moves are Return, Double Kick, and Flame Charge.
Zebstrika is no more priority weak than many common OU Pokemon. Even Adamant CB Breloom's Technician Mach Punch can't OHKO it from full health. Terrakion has more priority problems than Zebstrika does. Zebstrika is also
not outsped by a ton of the metagame. Seriously, if there's one thing that's actually
great about Zebstrika, it's its speed stat. It outspeeds every unboosted Pokemon in OU besides Alakazam, Dugtrio, and Jolteon.
Also, NU is not a "trash pit," it's a great balanced metagame. Up until March when Ubers had a sudden surge in popularity, NU was the third most popular balanced metagame out there (even now it's just barely behind Ubers).
As for Zebstrika in OU, it's not so much that it's underrated, just that it's plain bad. Special sets are the only remotely good ones, but that low base 80 SpA stat really weighs it down. Even if it manages to get a LightningRod boost, Zebstrika is still a tiny bit weaker than Thundurus-T, and the extra speed isn't that much of an advantage when Thundurus-T gets Agility (Zebstrika does too, but it's not really helping him outspeed anything that Thundurus-T wouldn't already beat at +2). Even as low as RU, I'd rather just use Manectric. It may be slower, but it still has a great speed stat itself, as well as a good deal more power, Switcheroo for Choice sets, and the option of using Flamethrower over Overheat on non-Choice sets.
Now, I would say that Zebstrika is a bit underrated in NU, although its usage has actually been on the rise lately since it makes a great check now to some of the new drop-downs. Zebstrika is one of the few Pokemon that can outspeed Scolipede without a Choice Scarf, and it easily OHKOs with Overheat. It also makes a decent check to Jynx, again OHKOing with Overheat. Another cool thing about Zebstrika is that it makes such a great Choice Scarf user due to its naturally high speed, letting it run a Modest nature and still beat positive nature base 100s. This includes the popular new Scarf Primeape, which Zebstrika can bring down if it comes in after Primeape uses Close Combat or if Primape has already taken ~40% damage, as well as the occasional Scarf Jynx.