Your team is mostly a fine balance, though some replacements are needed for Dialga as Necrozma Dusk Mane is a better Steel-type. Some moveset changes, and a check for Kyogre is what you all need.
Dialga --> Necrozma-Dusk-Mane
Necrozma-Dusk-Mane @ Rocky Helmet
Ability: Prism Armor
EVs: 252 HP / 252 Def / 4 SpD
Impish Nature
- Stealth Rock
- Sunsteel Strike
- Earthquake
- Morning Sun
Dialga defensively is outclassed by Dusk Mane Necrozma. This is because it has reliable recovery in form of Morning Sun, and its typing lets it deal with Zacian-Crowned much better. Dialga can't do that well, as it has to run a Chople Berry to not get KOed by Close Combat. Dusk Mane also has access to Stealth Rocks like Dialga, so it's fine replacing it with this. Rocky Helmet punishes physical attackers, notably allows it to 1v1 Swords Dance Zacian. Earthquake prevents it from becoming set-up food for Zekrom, which can just hide behind Substitute. Morning Sun is for recovery.
Yveltal
Yveltal @ Heavy-Duty Boots
Ability: Dark Aura
EVs: 252 HP / 4 Def / 252 SpD
Careful Nature
IVs: 25 Spe
- Foul Play
- Roost
- Defog
- U-turn
The EVs are for Specially Defensive Yveltal, but the moves aren't for it. Dark Pulse is outclassed by Knock Off, Foul Play and Snarl as a utility move on SpD set. Oblivion Wing lacks power without any SpA investment, hence is not as reliable recovery. So why not Roost? Heat Wave is also redundant on a defensive set, U-Turn seems to be much better for pivoting. 25 Spe IVs is so that you become slower than other SpD Yveltal to execute "Slow Turn".
Calyrex-Shadow
Calyrex-Shadow @ Life Orb
Ability: As One (Spectrier)
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Nasty Plot
- Astral Barrage
- Psyshock
- Draining Kiss
Focus Sash lacks power, so why not Life Orb? It allows Calyrex to OHKO SpD Yveltal with a +2 Max Starfall, so that's very helpful. Aside from that, Energy Ball is a bad choice as 1. Tyranitar isn't that used as Yveltal 2. The entire set is walled by Specially Defensive Yveltal. So, Draining Kiss should be used over that. Rest of it is pretty fine.
Calculations:
+2 252 SpA Life Orb Calyrex-Shadow Max Starfall vs. 248 HP / 252+ SpD Yveltal: 494-582 (108.5 - 127.9%) -- guaranteed OHKO
+2 252 SpA Life Orb Calyrex-Shadow Psyshock vs. 248 HP / 252+ Def Eviolite Chansey: 538-633 (76.5 - 90%) -- guaranteed 2HKO
+2 252 SpA Life Orb Calyrex-Shadow Max Starfall vs. 252 HP / 252+ SpD Tyranitar in Sand: 325-385 (80.4 - 95.2%) -- 56.3% chance to OHKO after Stealth Rock
Zacian-Crowned --> Eternatus
Eternatus @ Black Sludge
Ability: Pressure
EVs: 252 HP / 212 SpD / 44 Spe
Calm Nature
- Dynamax Cannon
- Flamethrower
- Toxic Spikes
- Recover
You really don't need Zacian-C when you already have heavy hitters like Calyrex-S, Landorus-T, and Kyogre. This team is really weak to Kyogre and lacks real switch-in, which can be fixed by adding Eternatus. Black Sludge maximizes recovery along with Recover, Dynamax Cannon is STAB. Flamethrower is for flaming them pesky Steel-types. Toxic Spikes provides hazard support. 44 Spe allows you to outsped maximum Base 90s, while the rest in SpD and HP to increase your bulk.
Landorus-Therian
Landorus-Therian (M) @ Life Orb
Ability: Intimidate
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Earthquake
- Fly
- Stone Edge
- Swords Dance
Landorus-T doesn't really need the bulk. Maximum Spe and Atk are almost necessary as to increase its wallbreaking capabilities. Protect is a waste of moveslot on a offensive Pokemon, and Superpower is not better than Stone Edge as Yveltal is more common than Ferrothorn. Swords Dance is also needed, to increase your power. Life Orb should be the standard option to deal higher damage.
Kyogre is fine. No comments.
Final Team
Hope this helps!
