There's no obvious Kings/Avs deal for Landeskog. Like has been said, Muzzin isn't young young. Not old, but not any more upside to his game. I don't know what happened to him this year, but he looked as shaky the few times he played in the World Cup as he has for the Kings basically all season.
If the Avs want a younger defenseman, the Kings have Forbort, Gravel, and then maybe a couple guys in the AHL. Clague played for Canada at the World Juniors. Forbort has finally become at least a non-1st round bust this year, but he's still only played 55 NHL games. Tough to know exactly what he is yet.
The issue there is that the Kings have a lot of cap space taken up, especially by Brown and Gaborik, and so a deal for any of those younger defensemen has to get more complicated, as the cap has to get figured out in that equation. I don't imagine the Avs have any need for Brown or Gaborik, even at 50%, so again, everything just gets more complicated.
If GM's want to do a deal, they can find a way to get deals done, but the Avs have the upper hand in this situation. Their season is all but over, and there's no rush for them to get rid of Landeskog. I don't know their exact expansion draft outlook, but I know the Kings risk losing someone they would rather not lose if they don't do anything. Plus they're sitting on the edge of the playoff race, and it could go either way. Lombardi has to make Sakic want to trade Landeskog to him, which isn't easy when you don't really have an upper hand any which way you look at it.