Here is my team. Not the one I used to beat her but it's a more efficient version.
And there is the details:
And state of Isogiku+Adlay team at the end of the fight:
As long as you run that Isogiku team (or any Adlay+Isogiku Easter+Pierce combo) you can't fail. They take care of one path and the main boss alone without taking damages (seriously, I never saw Isogiku goes under 535%HP). Dealing with the lmid boss of the other road is the only hard stuff left. Definitively harder than Adlay but far far easier than Honeysuckle. This one was a huge piece of boss.
If you don't have Adlay yo support Isogiku, Elder Flower Christmas may help you as long as you max the ATK/CRIT/skill rate debuff. If you don't take damages, you won't die.
If you don't have Isogiku Easter, then I guess you can pray and search for another effective way.
Feels like Isogiku is the actual boss here and Zinnia the hopeless player.