Lego is no longer allowing Zelda-themed sets on its Ideas service, no matter how much you want Hyrule Castle
It's reportedly due to a "licence conflict."
If you've ever been on Lego Ideas, you've probably seen some fan The Legend of Zelda sets. Well, not any more, as Lego has apparently banned Zelda ideas from the service.
If you haven't been on Lego Ideas, however, let me quickly explain it for you. Fans can submit ideas (get it?) for Lego sets, providing proof of concepts for what they might look like. Sometimes it's simple things like a car, but there have actually been some notable licenced entries, like a Steamboat Willie set. So of course, fans have attempted to get some Zelda sets through, but according to Brick Fanatics, that won't be possible any more.
According to Brick Fanatics, the issue comes down to a "licence conflict," which the Lego Ideas site notifies you of when submitting an idea as an existing IP. Brick Fanatics also provided an example of what it looks like when you attempt other IP, such as Mario Bros, which isn't allowed due to the already existing sets, or Pokemon, which also has a licence conflict, though in this case it's because Mega Construx (which you probably remember as Mega Bloks) holds the rights for brick-based creations.
Fans have previously attempted to get Zelda-themed sets through before, with some even getting through to the review stage, though obviously they've all been rejected.
There's a few possible reasons why Zelda submissions are no longer allowed. One, which would likely be everyone's preferred reason, is that Lego and Nintendo are actually working together on something for the series, which wouldn't be too surprising considering the Mario sets.
Another possibility is that a company like Mega Construx, or otherwise, holds the rights, which Lego is aware of behind the scenes, so can't allow any more Ideas sets on the site.
Alternatively, it could just be that Nintendo have expressly said it doesn't want to do a Zelda site, as there obviously has been communication between the two companies for the Mario sets. Maybe we'll never find out, though I personally wouldn't mind adding a Lego Hyrule castle to the collection.