I liked
Human's proposed format for these types of posts, so I'm going to give that a shot:
1. Why is the Pokémon a core part of the team? Why is it important?
Mega Salamence is a pretty splashable Pokemon, and on this team it just offers lots of role compression. Basically it offers Intimidate support (pre-mega), speed control through Tailwind, and is just a fast but also bulky attacker that can switch into neutral hits and apply offensive pressure on the following turn.
The set I went with was the standard dex analysis set, but with Fire Blast > Hyper Voice. I think the mence analysis is due for a refresh (mono Flying STAB is terrible in this meta) but I liked the calcs that the given spread accomplished; OHKO no bulk Lele with Double-Edge, then dump into SpA. Fire Blast allows Salamence to properly check offensive Steel-types like Kartana and Mega Scizor. It and also gives it coverage vs Mega Metagross, a Pokemon that otherwise threatens Salamence.
2. How do the other Pokémon support this? Very brief description of what each Pokémon offers (typing/special moves/etc.)
Ninetales-Alola is mainly to offer Aurora Veil support, which makes the rest of the team harder to take down. Salamence and Zygarde both hate being Intimidate cycled by Landorus-T, and Ninetales-Alola deals with Landorus-T. Being able to reset an opposing weather is also nice. I went with Freeze-Dry in the third slot to solidify Ninetales's ability to deal with opposing rain sweepers, as well as bulky Water-types in general (including Gastrodon).
Zeraora is basically the fastest Fake Out user in the game, so it seems like a safe choice for ensuring that Nintetales can set Aurora Veil during an opening lead.
Went with a physical set to explore its physical movepool a bit more, and went with Adamant > Jolly to boost its power a bit more. Much like how Modest Koko is now an acceptable set now that Mega Gengar is banned, I figured that Zeraora wanted more power over the sheer speed. Close Combat gives another tool to hit a variety of potential threats, such as Tyranitar, Incineroar, Kyurem-B and Kartana among others.
I wanted at least one set up wincon to take advantage of the added bulk that Aurora Veil offers, so I went with DD Zygarde here. The set here is pretty much just the standard one. I just like bumping Zygarde's speed up to 274 so it always outspeeds a Jolly Bulu, since it only takes 12 EVs to hit that benchmark anyway.
Tapu Fini offers added insurance against rain, gives another speed control option, and is packing Taunt to help shut down bulky wincons like CM Cresselia and Chansey, as well as Trick Room setters, etc. I've been experimenting a bit with a faster Tapu Fini - you lose the ability to survive two Mega Metagross Iron Heads, but you get to move before a standard Zygarde and hit it with a Moonblast or Icy Wind, which is nice. On this team specifically, you also get to move before your own Zygarde, softening up a target ahead of a Tectonic Rage kill.
Finally, I knew I still wanted a Stealth Rock setter and another Pokemon with Fire coverage to handle bulky steels, so Heatran fit the bill. Besides, this entire team is already a throwback to old meta picks anyways lol, so I thought why not.
3. What does the team need to do in order to win? Identify win conditions of any kind.
This team is more or less built to win wars of attrition through good positioning. Usually you want to attempt to set up Aurora Veil early on to give your team the bulk advantage. It's also ideal to get Stealth Rock set up early on to punish your opponent's passive switching.
Between the hail and stealth rocks, you should be able to wittle down your foe through passive damage while they struggle to break through a team of bulky attackers buffed by Aurora Veil.
You do have Zygarde in the back as a Dragon Dance sweeper, which in many cases should be preserved at high hp so it can pull off late game cleaning once its checks have been dealt with (namely intimidate cyclers like Lando-T and Incineroar).
The whole team is a bit shaky versus Kyurem-B, so if your opponent brings that, try to deal with it sooner than later. Likewise, Chansey can be a bit difficult to break through before opposing Intimidate cyclers are dealt with, so if you match up versus a Chansey it's probably best to focus on the partners first until a late game scenario. Tapu Fini to Taunt the Chansey is probably your best bet if you need to control it in the mid game.
But yeah, overall this probably isn't the best team out there but, for the amount of time I spent building it I feel this is at least a fun team that can pull through in a seasonals match if need be. Have fun using it and let me know if there's a way to make this better :)