For many courier companies (FedEx, Toll etc) it's a requirement to include a Contact Name, along with a Contact Email address when shipping goods to a shipping address.  There is often a requirement to identify if the consignment is being shipped as "Available to Leave" or ATL which must be marked on the label/consignment note, and there is often rules around deliveries to residential addresses (FedEX Australia for example charge you additional fees for consignments over 30kg).  

I suggest the following fields are added to the Shipping Address as they specifically relate to/belong to the Shipping Address (not just the customer record).  If a customer has several shipping addresses, the information is often different for each address.

Contact Name    

A field to enter the Contact Name.  We use the 'Attention' to specify the shipping address 'name' (business name, building name etc) so there needs to be a field for both 'company name' which may be different from the customer name AND the contact.  

Contact email address

A boolean field which can be passed through to shipping to identify if the consignment can be left at the indicated location.  

A boolean field to identify if this address is treated as a residential address for freight/shipping purposes.

A long text field where information like acceptable delivery times and days or delivery instructions can be included.

I recognise that custom fields can be created in Zoho, but "Customer" custom fields aren't related to the shipping address so table so it's not possible to include the data for specific shipping addresses.