It's the first game yes, but what more important is that the show is great, Wayforward is great (developers behind Contra 4, shantae and more recently Mighty Switch Force)I don't know that show.
Is it the first game from that show on a console? I'm curious to test last games if there were any.
and when you combine those things with Zelda II gameplay your bound to have something good come out of it.
Another thing I should mention is that the shows creator himself (Pendelton Ward) will be supervising the project, so unlike many other TV to game releases this will actually stay true to the show.