I hope you are a new player cause there is a lot of changes.
Mewtwo : Change nature to Timid,Set Evs to [252 SpA 252 Spe 6 HP]
Change Poison Jab to Aura Sphere for coverage.
Maybe change Recover for Thunderbolt or Ice Beam.
Zamazenta Crowned is kinda bad so swap it for
Necrozma Dusk Mane ( Yes I know it will overlap with Mewtwo) or
Magearna.
Sooooo, Here's moves to both
Necrozma Dusk Mane (Weakness Policy)
Evs : 252 Atk 128 HP 128 Spe
- Sunsteel Strike
- Photon Geyser/Psychic Fangs (Reliable Stab/Breaking screens
- Earthquake (Coverage)
- Dragon Dance (Stat Booster)
Magearna (Aguav Berry)
Evs : 252 HP 252 SpA 6 SpD
Nature : Calm
- Heart Stamp (Great against both Calyex and Geomancy Xerneas)
- Dazzling Gleam/Fluer Cannon (Reliable Stab/Risky Stab)
Flash Cannon (Reliable Stab)
- Thunderbolt/Ice Beam/Calm Mind/Shift Gear (Coverage/ Boosting Move)
Sorry Silvally Fans but it is outclassed by many other Pokémon.
For this set I prefer Groudon.
Groudon (Leftovers)
Evs :252 HP 252 Atk 6 Def
Nature : Adamant
- Earthquake/Percipice Blades (Great Stab/More Power but less accurate)
- Fire Punch (Grass And Ice Coverage + Drought Bonus)
- Rock Slide (Flying coverage)
- Dragon Claw/Shadow Claw/Bulk Up (Coverage/Boost)
Kyurem-Black is outclassed by Zekrom. Sooo,
Zekrom (Leftovers)
Evs : 252 Atk 128 HP 128 Spe
Nature : Jolly
- Fusion Bolt/Bolt Strike (Reliable Stab/More Power but less accurate)
- Dragon Claw (Weaker Stab than Outrage but no confusion)
- Dragon Dance (Great Boosting Move)
- Roost (Reliable Recovery)
Xurkitree is useless when Zekrom is around.
So I suggest you Yveltal to kill Calyrex-Shadow.
Yveltal (Heavy-Duty Boots)
Evs : 248 HP 252 SpD 8 SpA
Nature : Calm
- Snarl (Hits through substitute)
- Oblivion Wing (Stab and also recovery)
- Defog (Gets rid of Sticky Web and Stealth Rock)
- Roost (Recovery)
Registeel is useless when Necrozma Dusk Mane/Magearna Is there.
So go with Cinderace/Blaziken for Stab Fire is always great.
Cinderace (Lansat Berry) [Libero]
Evs : 252 Atk 252 Spe 6 Def
Nature : Jolly
- Pyro Ball (Great Signature Move)
- Sucker Punch (Priority)
- Zen Headbutt (Coverage)
- U Turn (Switching)
Blaziken (Custap Berry) [Speed Boost]
Evs 252 Atk 252 Spe 6 HP
Nature : Jolly
- Blaze Kick/Flare Blitz (Reliable Stab/More Power but recoil)
- Brick Break/Close Combat (For Screens/More Power but defense drop)
- Thunder Punch (Water and Flying coverage)
- Earthquake (Coverage)
PHEW that's over.
If I missed anything please comment