In order to make Zushuka mortal, you need first to hit her a couple of times, even though she won't lose HP, some pickaxes'll appear on the ice altar in the center of the respawn.
As soon as you see the pickaxes, take them and destroy the ice cubes that'll appear on the right and left side of the altar (you need to get a little bit far away, but it really is the only place you can go).
After all ice cubes are destroyed, Zushuka will change her hair colour from blue to white and now she'll be mortal.
Don't forget that once her HP is getting red she'll heal her HP to its fullest one time before you'll be able to finish her
Even though a player level 150+ should be able to kill her alone, since its a rare respawn it's worth calling other boss hunters of your server to go, so you can be called to go too.
