When I create a contact in Zoho Mail's "Contacts" system, it only allows me to choose from the Zoho-permitted list of phone labels: Mobile, Home, Work, Fax, or "Others".  Coming from Gmail, Outlook.com, Microsoft Exchange, and others, I am used to specifying custom names for phone numbers.  For example, I may want to name a phone number on a contact "Main Office", Front Desktop, Scheduling, Customer Service, Sales, Account Rep, Unknown, John Smith, Jane Smith, Bob's Office, Test Line, Florida Branch, etc.

It would be extremely helpful to have this feature in Zoho, and I've waited years for Zoho to support it.  I think the version of the Microsoft Exchange protocol Zoho uses to sync contacts to iPhones supports custom labels already, so I hope Zoho can get that feature working soon.