Chun-li casting copies

When [[Zethi, Arcane Blademaster]]/[[Chun-Li, Countless Kicks]] attacks and copies the spells in exile and allows you to cast them, do you:

• Cast the first one and cast the rest in response on the same stack
• Get priority to cast one spell, resolve that stack, then regain priority to cast another
  • If this is the case, can you then cast some/all of the copies in response?