Custom passwords
From Zen Cart(tm) Wiki
Overview
When a customer forgets his or her password, Zen Cart™ will generate a new one. By default, this password is a mix of digits and characters such as Mx53e9. You can restrict this to all digits or all characters, however.
How to do it
Open the file includes/modules/pages/password_forgotten/header_php.php and find the following line (line 35 in an unmodified copy):
$new_password = zen_create_random_value(ENTRY_PASSWORD_MIN_LENGTH);
Change this to either:
$new_password = zen_create_random_value(ENTRY_PASSWORD_MIN_LENGTH,'chars');
or
$new_password = zen_create_random_value(ENTRY_PASSWORD_MIN_LENGTH, 'digits');