If you like, you can head out of the city to the West and have a look at the iced-over Route 9, but there’s nothing new to actually do there.  Route 11 to the East has been similarly glazed over to boot, but you really don’t need to do anything there either.  Instead, head back to the East side of the city and follow the street North to encounter another of Plasma G’s members.

Battle: Team Plasma Grunt (1760 Poke)
Opponent: Watchog Lv 44, Muk Lv 44

Hit the North side of town and turn West and you’ll quickly run afoul of more of Team Plasma.

Battle: Team Plasma Grunt (1760 Poke)
Opponent: Golbat Lv 44, Garbodor Lv 44

When you arrive at the Gym with all of Team Plasma defeated, Zinzolin is waiting outside the front door of the building.  He’s cold and miserable- but at least this is proof he’s alive, he thinks.

Battle: Team Plasma Zinzolin (8640 Poke)
Opponent: Cryogonal Lv 46, Cryogonal Lv 46, Weavile Lv 48

Staggered by the improvements you’ve made since Lacunosa Town, Zinzolin opts to give up, uncomfortable in the cold weather, and leave.  He gives you some parting food for thought, though- what would it look like for all Unova to be shrouded in ice?  According to the Sage, Team Plasma G is willing to do anything to see that achieved, and therefore to get ahold of the Splicers.