Okay, let me expand:
Zelda will still increase attendance at IoA, no matter when it happens, before or after Mario. New attractions (almost) always increase attendance. The Legend of Zelda is an iconic name that people will show up for. Coming before or after Mario doesn't affect the number of people who will go to IoA for it.
If it happens before Mario, Nintendo/Zelda fans will show up as well as guests just looking for new stuff to do, and then when the larger Mario crowds come to Orlando they'll say, "Oh the other park has Zelda, let's see that one too!"
If it happens after Mario, it means that only second part of the paragraph above will happen. Either way people are coming to see Zelda. Its placement in the timeline is irrelevant.
This is exactly correct. It will sell less. It's also irrelevant to the conversation.
When Zelda is built will not affect its impact. Its impact will be the same if it comes before or after Mario.