If you prefer not to use the standard method of sending API requests, you can always download this script, which gives you direct access to all the files needed for installing an SSL certificate.
When you issue a free SSL certificate through us, whether it's Let's Encrypt or ZeroSSL, you will receive the necessary files to activate the certificate on your server. These files include the private key and the certificate itself.
The official documentation can be found on our GitHub Repository: https://github.com/ClouDNS/cloudns-api-bulk-updates/blob/master/download-free-ssl/download-free-ssl.php
The script is made to work for sub-users automatically, but you can always change it to be used by users. This can happen by replacing the $api_url parameter "sub-auth-id" with "auth-id" only. You can create a new API user/sub-user or export the information from an already existing one from the "API & Resellers" tab in the logged-in account.
$auth_id = 'XXX';
$auth_pass = 'XXX';
The script can be executed by using the standard command for reading a file, such as:
php download-free-ssl.php
Do not forget to access the file directory (path) first.