Loved this! Had a first run where I finished the Mario pretty much without advancing the Zelda part, I was starting to think that the combo theme was a bit weak in the gameplay (because it seemed more advantageous to just do one game at a time). But then the timer started and I rushed through the Zelda part, failed and lost xD
I really loved the art, it's very cute, and there's a lot of it! It gives off the same vibe as the original games, although a lot of the assets are more detailed and the color palettes are quite different (but in a good way, at least from what I remember). So great job there!
The concept is very cool, and contrary to what I've read in other comments, for me it pretty much falls under the "combo" theme. Not in the usual meaning it has in video games, but because you need to win two games at the same time, which is a cool take on it!
I guess the theme would have been even stronger for me if I really ended up moving in both games *at the same time*, but it was too hard for me. I almost always alternated between one and the other.
Still, impressive entry, I really enjoyed it! :3