Hello! I have registered DDNSs to my own Dynu account. Now I need to transfer it to a corporate account. How can I do this?

You could either delete the domain from the current account and add it again to the new account (provided that the domain does not have many DNS records) or you could open a support ticket to have the domain moved. I have done both before and did not run into any issues. When opening a support ticket, do so from the original account and provide the domain name to be moved and the new account username/email address.