This is everything you need to know about how to recruit Zoah in Chrono Cross: The Radical Dreamers Edition.
How to Recruit Zoah
You’ll come across the option to recruit Zoah as part of the main story. However, the choice will leave you missing out on someone else — for a brief time.
You will be given a choice when rescuing Riddel in the story (during Termina: Another World). You can either choose Karsh or Zoah to go ahead and rescue Riddel, and whichever you choose will become a party member.
The other one will become a party member later.