Can someone explain the ZA ranked battles?

I'm adding to the points side of this

You also get points for landing super effective hits

Also, here's something for team building, everyone has been using Dragon type, normally Garchomp or Salamence, and a Metagross lately

I've also seen a lot of Excadrill

The reason why is because the Dragons are extremely strong and can tank hits easily

The Metagross covers the weakness to Fairy and Ice types

Excadrill is able to take hits and deal massive damage, especially with its new Mega. It also has the advantage over Fire types because of its Ground side. It is also powerful against Pokémon like Charizard that don't take Ground damage and are Fire because they often teach it Rock Slide.

For the Dragons, I would advise an Ice type. The Dragons used are often dual type and both are usually weak to Ice. That explains the increase in use of Glaceon (I know I didn't mention that above, but it's true). That or a Fairy that can Mega

To counter Metagross, which often knows Earthquake, I'd say Charizard. It can learn Fire moves, Crunch, and Dig, making it quite good against Metegross.

Excadrill is hard to say with it being strong against Ice and Flying, two that have advantage over Ground, and over Fire, a type with advantage over Steel. I'd probably say Gyrados due to it being a Water type. Plus, it can normally take a lot of hits, so even if Excadrill uses Rock Slide of should handle it once or twice. But that Rock Slide won't be an issue once you Mega Evolve, Gyrados losing its Flying for Dark.

Hope that was helpful!