Z Celesteela makes for a nice set-up sweeper since it has respectable bulk even when uninvested and outrusn a lot of the unboosted meta after an autotomize. Modest reaches 402 speed at +2, which outruns Koko and the like but falls short of the base 135s (which aren't released yet in the cases of Mega Lopunny and Mega Manectric). After getting a KO it can usually steamroll through a weakened team. The set is straight from analysis; I chose EQ over Giga Drain since it cucks electrics and my team handles bulky waters/grounds well already.
Mega Pinsir is here to punch holes so Steela can clean up later. Chansey and Toxapex can handle Steela, but +2 Mega Pinsir tears them apart. It also offers priority for certain threats that outrun +2 Steela, such as Mega Zam, Pheromosa, weakened scarfers, etc. Standard set yet again, with EQ over CC for Mega Metagross (if Pinsir lives a hit somehow), Toxapex, and AV Magearna.
Excadrill was added since the core is very weak to electrics. Although I love Scarf Drill, the bulkier option allows it to better check electrics and spin/set rocks over the course of the game. I went with max HP and max speed since the added special bulk is not too needed, whereas the speed is very nice. Eventually I might try a different spead that lets Drill outrun max speed Timid Heatran and stick the rest in Special Defense, but this is fine for now. Mold Breaker lets me get rocks up versus stall and get Toxic on Mega Sableye. The usual coverage options work nicely.
Thundy is the third of the birds, and offers a powerful Thunderbolt to smack bulky waters along with good coverage options. "But wait!", you ask, "Just use Tapu Koko instead!" That's where you're wrong, kiddo. While Koko's speed and pivoting ability is fantastic, Mixed LO Thundurus is amazing since it baits the hell out of AV Tangrowth, Chansey, Alolan Marowak, and other mons that traditionally soak up Thunderbolts and annoy the rest of my team. Abusing Defog is really handy for dismantling slower teams. It helps the team pressure stall immensely, and its speed tier lets it outrun Mega Metagross and other base 110s. Its uses LO better than Koko does, so HP Ice can reliably beat Lando-T, offensive Zygarde, and Garchomp. Another ground immunity is dank too.
Banded Zygarde comes in as another electric deterrent that can break holes with Banded Thousand Arrows, or Outrage if resists are KO'd. Banded Extremespeed is another powerful priority that gives me insurance against Ash/Protean Greninja, Volcarona, Scarf Nihilego, etc. Toxic is for Tangrowth, Lando-T, and Shedinja mostly. Iron Tail could be useful against Unaware Clef but idk. Max attack max speed Adamant as usual, not sure about where the last 4 EVs should go.
Where would any offense team be without Greninja. It offers plenty of speed and firepower to the team, with Hydro and Ice Beam to punch holes and generally keep the opponent's mons low. Gunk lures Fini and Clef since they're annoying, and it also pairs well with Spikes, as the team really appreciates the chip damage for KO's. HP Fire would be great if I can fit it in somewhere. Spread is standard.