Exporting a mixed resolution timeline with 1080p and 4k footage for DVD

I did a three camera shoot with two 4k cameras and one 1080p camera and upscaled the footage by setting to frame size.  However the client wants DVD's for this project so I am trying to export the footage in a dvd friendly format "high quality 480p SD wide."  When I play back the file the 4k footage looks fine but the 1080p footage looks like it was shot on VHS in 1985.  I expect the overall footage to look not great since it's going to dvd but the 1080p footage looks really bad compared to the rest.  Is there something I am doing wrong and is there a different setting or a workaround?  Is the program doing the same amount of downgrade to the 1080p footage that it's doing to the 4k footage and is that what is making it look so bad?  Any help would be greatly appreciated!