how to encode a 6 track recording in a single discrete 5.1 track

[outsider]

hi, this is my first post here, i record with alesis Hd 24 or fostex pd6, and I do multitrack postproduction with Nuendo,

please Now i want to know how to export tracks in a one track 5.1 and to realize a video dvd to be played in an home dvd player with surround system.