I think it's safe to assume that Amazon has a reason to not "leverage" Zappos, e.g. maybe Zappos margins are much lower or there's substantial upside to having

I think it's safe to assume that Amazon has a reason to not "leverage" Zappos, e.g. maybe Zappos margins are much lower or there's substantial upside to having people shop on the main Amazon site and throw some electronics in their cart while they're at it.