If you are trying to import customer information from another application into ZenCart database, the linked forum thread may be helpful. The thread has an tool that uses the Zen-Cart built-in function zen_encrypt_password() to convert a plain text password into the MD5+salt encrypted value that ZenCart stores it as in the database.

Also look at the database schema because you may need to populate records in the customers and customer_info and address_book tables.