Rotom-Frost @ Choice Scarf 
/ Icium Z
Ability: Levitate
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Volt Switch
- Blizzard
- Trick / Pain Split
- Thunderbolt
Rotom-Frost is ZU's best offensive pivot, bringing with it STAB Electric/Ice coverage and useful utility such as trick or pain split. This allows it to do a good job of presenting a threatening offensive presence and forcing switches, and having Trick allows it to cripple Taunt Vigoroth. However, while Rotom-Frost may excel offensively, it's poor defensively. Notably it's weak to Fire and Fighting typings, meaning that it's highly threatened by Pokemon such as Monferno and Combusken.

Mareanie @ Eviolite
Ability: Regenerator
EVs: 248 HP / 240 Def / 20 SpD
Bold / Impish Nature
IVs: 0 Atk / 31 Atk
- Toxic / Knock Off / Scald
- Toxic Spikes
- Haze
- Recover
Mareanie steps in to handle Rotom-Frost's weakness Fire and Fighting typings, countering Combusken, Monferno and Silvally-Fighting while setting Toxic Spikes to punish the switches that Rotom-Frost forces. Rotom-Frost meanwhile is immune to Ground type attacks for Mareanie and threatens strong grass type attackers that might otherwise try to break through it on the special side. Having Haze in particular allows Mareanie to also pair with Rotom-Frost to give a player an answer to both of the notable Bulk Up Vigoroth sets.
---Teambuilding Weaknesses---
This core does not appreciate bulky Psychic type Pokemon with Fighting or Fire type coverage such as Grumpig. Ground attackers that can KO Rotom-Frost such as Golem are also highly problematic for this core, as are strong Fire type attackers that can still significantly damage Mareanie through coverage such as Rapidash with a damage boosting item. This core also especially does not appreciate powerful special attackers that can break right through Mareanie such as Lurantis or common Knock Off abusers such as Crustle or Kecleon that remove Mareanie's Eviolite and threaten Rotom-Frost. Bulky setup sweepers that can avoid punishment from either Mareanie or Frost while still dealing significant damage such as Sub SD Bouffalant are also problematic.