Quickbooks API - GET works POST does not

I am trying to set up a zap which will create an estimate in Quickbooks Online and then SEND the estimate.

The currently available actions inside the Quickbooks Online integration allow to create an estimate.  There is no action to SEND the estimate though.  This is a previously requested action almost a year ago.  I have finally given up on Zapier integrating this request and so decided to attempt it on my own using the HTTP request action.

Using the HTTP request action I can successfully perform a GET request:

The above results in the expected JSON return showing all the estimate information.  This proves the authentication is working.

Per the Quickbooks API docs, in order to send an estimate it needs a POST request in the following format:

POST /v3/company/<realmID>/estimate/<estimateId>/send
POST /v3/company/<realmID>/estimate/<estimateId>/send?sendTo=<emailAddr>&minorversion=65

Content type:application/octet-stream
Production Base URL:https://quickbooks.api.intuit.com
Sandbox Base URL:https://sandbox-quickbooks.api.intuit.com

However it fails for unknown reasons:

{
  "request": {
    "method": "POST",
    "url": "https://quickbooks.api.intuit.com/v3/company/9130354169095986/estimate/546/send",
    "querystring": {
      "minorversion": "65"
    },
    "headers": {
      "content type": "application/octet-stream"
    },
    "body": null
  },
  "response": {
    "status": 400,
    "headers": {
      "date": "Fri, 14 Apr 2023 23:20:08 GMT",
      "content-type": "text/plain",
      "content-length": "11",
      "connection": "keep-alive",
      "server": "envoy"
    },
    "body": "Bad Request"
  }
}

Please advise how to SEND an estimate.