Is Zeroara still viable in OU despite being in UU? If so what sets could it run?
To add onto Katy's great answer, I would like to offer you some potential options that it runs to try and stand out.
As she said, it faces a lot of difficulty in the tier currently due to the infestation of Landorus-T, Garchomp, Swampert, and other good Ground-types that stone wall its onslaught, as an Electric-type breaker it is fairly outclassed, and as speed control, Pheromosa and Choice Scarf Spectrier wholly trump it.
The best way to use it, in my opinion, is as a utility pivot, utilizing Knock Off and Toxic as a way to capitalize on the Ground-types it invites in. Unlike its competition, its access to Knock Off, Toxic, and its notable speed tier over Dragapult does give it a niche. Knock Off is a phenomenal move in the current metagame, able to strip many Pokemon of their valuable items, and it is a great way to pick off passive healing from Swampert/Landorus-T, as well as Choice items that could enable revenge killing or more effective breaking from opponents. Toxic is also a great option, which lays out a lot of pressure against the many Ground-types in the metagame which hate its recoil in the long term, especially since all barring Hippowdon lack reliable recovery.
Of course, Volt Switch is always a good option as well, and in tandem with HDB it can help to decently facilitate Pokemon such as Pheromosa and Melmetal that appreciate smoother switch-in opportunities against targets such as Rillaboom throughout the course of the game.
Thanks, but is Politoed still a viable option?
Politoed with Drizzle is always cool, and as stated, its Stealth Rock neutrality/access to Encore are neat standouts to give it more setting opportunities. Though, unlike Pelipper, its lack of momentum, lack of reliable recovery, and lack of a resistance/immunity to Fighting-types and Ground-types respectively hamper Rain teams' much needed momentum to keep up the pressure throughout the course of the match. Politoed also just doesn't synergize with Rain cores as well as Pelipper does. Though, you can certainly give it a try as a backup Rain setter!