This is the team I used, I was able to set up 3 DDs and sweep Yuki with Haxorus, Using Mew to spam Calm Mind and Rock Polish and Baton Passing to Mega Eevee swept everyone else. Good luck.
D. Venu should be Timid, 252 Spe, 252 SpA, 4 Def, with a moveset of Calm Mind, Psychic, Shadow Ball, and Moonblast, with the appropriate megastone. That itself should be able to sweep the E4. D. Gallade wants a Choice Scarf, and the Jolly Nature. D. Spidergross wants max HP, max Atk, Adamant, unless you mega, which wants Jolly, max Spe max Atk. The moveset should be EQ, Rock Slide, Knock Off/Superpower, U-Turn. On Tyranitar, just go Max HP, max Atk, and replace Giga Impact with Superpower or Brick Break. Give D. Haxorus the Life Orb, as well as a Jolly Nature. One last tip, get everyone to the same level, since the E4 scales to your highest level mon.
This would be a great solution if I had delta ditto but sadly this is for a first elite 4 run and I just want a completion before I go fully best possible nature stuff as I can’t really do it without pokepon and thats just hell.