Ok, I emailed with Apple and even spoke to the developer support about this issue. There is absolutely no way to transfer an app that uses or has used in a past version iCloud to another account.
This leaves you with these 2 options suggested by Apple:
- Rename your complete iOS account, but this is only possible if your company has undergone a legal name change. Contact support if you want to do this.
- Delete your app and free the app name and re-upload the app in your new account. You will lose the ability to update current users. https://help.apple.com/app-store-connect/#/dev28d17ed35 (Deleting an App)
Too bad.