There IS payment link API, it's just not documented.
If you POST something like
{
"customer_id": 123456000001234567,
"payment_amount": "1.00",
"expiry_time": "2022-04-30",
"description": "TEST"
}
to https://books.zoho.[eu]/api/v3/paymentlinks?organization_id=123456
you will get a new payment link with default contact email and status "generated". You can get URL from the response->payment_link->url
.
Unfortunately, I didn't find out how to change the status of the payment link.
You can also send an email with POST to /api/v3/paymentlinks/{paymentlink_id}/email?organization_id=123456
if you specify subject, body and to_mail_ids array, and also do changes with PUT to i.e. expiry_time, but it would be great to know how to mark payments.