The expiation is to feed ten poor people or to clothe them. If you are unable to do this financially, you must fast 3 days and you can do them now.

I have broken an oath. And accordingly I have to fast for 3 days. But can I keep the Sunnah fast of dhul hijjah first and then later fast the 3 days for breaking the promise? Or are the 3 fast more important than Sunnah fast?