I'll cut right to the chase and start with the minor changes
Use boots on Weavile. Based on your team, I would imagine that you're still new to the tier. If that is the case, then stick with the default. Not using boots on Weavile would leave you vulnerable to rocks and unless you really know what you're doing, do not go for greedy items on this thing. You should also replace fake out with ice shard. You do not want to be that helpless against Koko, Zeraora and Dragapult
The set is ok. Just use yache berry as its item. You're not running hyper offense so there is no need to run life orb. Yache would allow you to ensure that opposing Weaviles won't stop your sweep short and also gives Garchomp a supporting role in luring in and killing Buzzwall for Weavile. Also, use rough skin. Sand veil is completely worthless on Garchomp because it's a huge waste
If you are gonna use metal birb, use the default set. Do not use offensive metal birb because those hard suck balls and you still lose to Magnezone either way. Using the default set would allow you to play around most of the physical attackers. You already have enough offensive mons as is and since you have metal birb on your original team, I would imagine you don't wanna use hyper offense
Now, for the major changes
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Chandelure is completely outclassed by Blacephalon as a fire / ghost type. Blace has a far stronger offensive stat and speed. It is much frailer in return but you won't be using this to take hits. You will be using this to crack holes in the enemy team. Sure, no energy ball means Tyranitar will grief you but Tyranitar itself isn't too common
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Given the team structure, there is literally no reason for Magnezone anymore. Instead, just use the king of the tier. It provides you with a rocker, a Garchomp buffer and a Heatran switchin all in one. Access to a switch move would also allow you to position your three offensive mons to attack
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Heatran is a very strong mon rn but atm, you don't need it. Pex would allow you a switchin to Urshifu, which would otherwise destroy your team provided Corviknight's helmet has been knocked off. It can also aid in defending your team against the likes of Dragapult and Weavile which would ease the pressure off Lando and Corvi thanks to regenerator
Here is the team. I should warn you, if you are anywhere below 1400 elo range, then do not expect to have much success with this team. It is built to handle the common metagame and in > 1400 elo, which is elo hell, a lot of players do not use the metagame pokemon which can give you a lot of trouble. Above 1400 elo though is where players finally begin to use the pokemon that are part of the metagame so this team will do just fine
