ZohoBooks API issue for creating an estimate

It looks like the current ZohoBooks API for creating an estimate, as documented at https://www.zoho.com/books/api/v3/estimates/#create-an-estimate, has some bugs or issues, as follows:

It's for a UK-based business.

Using the

url='https://books.zoho.com/api/v3/estimates'

method='POST'

params='&ignore_auto_number_generation=false'

we submitted this:

data='Array

    [customer_id] => 1984178000029361071

    [date] => 2024-06-17

    [expiry_date] => 2024-08-17

    [reference_number] => Quote Request

Naomi Fux

    [line_items] => Array

            [0] => Array

                    [item_id] =>

                    [name] => Fast Delivery Sneeze Screen and Cake Display

                    [description] =>

External Dimensions : 600w x 310h x 300d in 10mm clear toughened glass

Base : Customer to silicone fix to worktop

Number of Shelves : 2

Shelf 1 Spacing : 87

Shelf 2 Spacing : 87

Shelf 1 Type : Full Depth

Shelf 2 Type : Full Depth

Sliding Doors : No

LED Lighting : No

                    [rate] => 425.00

                    [quantity] => 1

                    [unit] => qty

                    [item_total] => 425.00

                    [product_type] => goods

                    [tax_id] => 1984178000000764068

                    [tax_name] =>

                    [tax_type] => tax

                    [tax_percentage] => 0

    [notes] => Hello,

Do you offer shipping overseas? I have been looking for this display and cannot find it in the States.

Thank you.

    [discount] => 0

    [vat_treatment] => overseas

    [is_inclusive_tax] =>

    [discount_type] => entity_level

But got this response:

response='Array

    [code] => 111876

    [message] => Sales to Non UK customers must be zero rated.

We correctly submitted a zero-rated vat_treatment for overseas, hence it should not come back with this error message when the customer is from overseas (United States in this case).

Can you please advise us how to implement a workaround for this? Or fix it on your end?

Thanks