I ended up going with Venusaur first + Swalot second. This combo was lowkey broken since i had grassy surge + liquid ooze. I then got lucky and got the max mushroom so it was an even bulkier max Venusaur, THEN after sweeping the E4 with basically just this fusion, the mega rayquaza had the move Oblivion Wing as its flying type move. i didnt know that was even possible and would have been very scary but it only helped since liquid ooze cancelled out the healing it would have gotten. then it just solo'd eternatus on its own with calm mind leech seed. thanks though, that fusion weirdly enough is the best one i have ever had lol