Simple question really, I recently bought both at the same time and wondered which to play first. Which one?

BTW: Can you use the codes multiple times?

Codes? I'm not sure what you're referring to. But the order really doesn't matter. They are entirely independent of each other and very unrelated. That being the case, because it doesn't matter, you might as well play it in the order the developers intend them with their release dates. So just play Dead Money first.

The redemption codes, but it doesn't really matter, just thought I could possibly lend it to my friend.

I was thinking Dead Money first too so that I can go to the wide open spaces of Honest Hearts right afterwards.

The redemption codes are a one time use.

As for which DLC to do first, it depends on preference: Do you want a spooky "Die at any time" experience first? Or a "Whoa, this is beautifu- OH MY GOD WHAT IS THAT THING!?" experience first? (referring to the Ghost of She/Giant Green Gecko. Though one can argue that Zion can have a survivalist feel to it. I like my version better. :hubbahubba:

Well, I think DM is going to be first just because I don't think the Mojave will be beautiful enough after being cooped up for so long, and Zion will meet that preference.

I would do DM first just to get the Holorifle. That's one badass gun when fully modded, repaired and your EW skill is maxed.