It's been a minute since I finished Act 3 but if I remember right, I've always tried the nice route. Meaning I usually prioratize my party over items. I aslo remember Zephyra takes a hit for Kuro and Kuro begs you to do something, and through protagonist plot armor (Sorry Strive, but until you can explain why the main character is basically "The chosen one" this is plot armor, or some kind of equivalent to it) you hug Zephyra, and she comes back to life. I don't think you get the artifact though, so you basically choose to get 3 party members in Zephyra, Kuro, and Jean, or getting an artifact, and maybe Kuro and Jean only. Again, I always prioratize characters over items, so maybe you can have it all, but I haven't figured that out yet.