Hi there! I am part of a company that sells products to other businesses that provide contracting services to their customers. I'd like to start storing a list of zip codes for each customer to track their territories and offer referrals. Some customers would have 8000+ applicable zip codes while others may have only 20. They are typically given to us in xslx or csv format. What is the best way to store these on a customer record and easily add mass amounts of zip codes to a customer record at once?

Thank you! ☺️