There is an SCI engine being worked on for ScummVM, so far it is a work in progress. Therefore it may eventually be possible to play these games on the DS. Also, the DS has very little RAM and CPU power, so either of these may stop it from working.
I generally only work on completed engines on the DS port, and there are plenty of those to keep me busy, so SCI is going to be a little further off.
As for Return to Zork, it's a completed engine, so is on my list to look at, at some point. This stuff is incredibly time consuming though, and I'm doing the DS port on my own, so you may have to be patient.
Subforum for discussion and help with ScummVM's Nintendo DS port
Moderator: ScummVM Team