Mega Latias has psyshock so it can win a setup war against magearna and volcarona (yes its that bulky) and ice beam is to revenge kill lando chomp and glisc. I don't think there's any more explaining that should be done.
Gliscor is the normal thing but with 24 speed instead of 20 speed to outspeed tapu fini. Again, don't really think there's any need to explain anything else about it.
Clefable is the rocker because it can kinda handle kyurem and dragon dance dragapult. And other rockers will double up on weaknesses. Clef has moonblast, stealth rock, and soft-boiled for obvious reasons with thunderwave because para is nice versus pretty much anything and it helps gliscor and latias outspeed more stuff.
Toxapex is here because it counters a whole lot of stuff and baneful bunker pex is one of the best ways of dealing with the acevish core thats really good right now. It also checks and/or counters a lot of other stuff too like mega lopunny, non earthquake zard x, zard y, some variants of kommo-o, blacephalon, hawlucha, and melmetal.
Magnezone is here because it traps mega scizor, corviknight, and skarmory which can be problematic for mega latias and gliscor. Scizor can wall latias and threaten to u-turn, and corv and skarm wall gliscor. Zone traps them and gets free subs off of them.
Landorus is great at role compression. It's here because it is speed control and defog. It's not really the best defogger but it's still kinda decent. It also hits very hard and has u-turn to be a pivot.
Clef can kinda handle kyu but it isn't really the most reliable counter.
Mega pinsir is a big threat to this team since after it swords dances not really anything on the team can kill it except for maybe mega latias who might live a return.
Latias is the only counter I have to this thing and latias hates taking u-turns or knock offs.
Boltbeam magearna kinda destroys this if latias gets taken out or if it gets boosts.
If tapu lele gets one correct focus blast predictionthis team is kinda screwed.
Thats all I can think of right now but there might be more idk