'Some creators refuse to fade.' The3Dude has been creating Zelda ROM hacks since 2017, reinventing a classic game for fans who have been itching for more content from a time when DLCs were just a pipe dream. His last hack, Perils of Darkness, was intended to be his last, but after slowly learning how to ASM hack in secret, he has released a new hack called the Mirror of Worlds with an entirely new gameplay system, with ' new in-game behaviors and transformations'.
According to the official project page, 'Mirror of Worlds combines all of Zelda 1’s Quest 2 data into a single massive playthrough, utilizing the full potential of the game’s memory.' The result is a game heavily centered around dungeons with Metroidvania elements. You'll get certain items from new dungeons instead of Sage's Crystals (a replacement for the Triforce pieces), though you will need to find 8 before entering the final dungeon, just like in the original game.

One thing I love about this hack is that when you download the file to patch onto your existing (legally sourced) ROM of The Legend of Zelda for the NES, you can choose from files with three different difficulty modes - Traveller, Hero, and Legend. As you might have gathered, Traveller is the easiest, with Legend being the type of difficulty that would make you want Ganon to gore you and get it over and done with.

The3Dude has opted to give the game a 16-bit feel, with brand new dungeons, a larger version of the Lost Words, and a new overworld for players to explore. And thanks to the ASM hacking of the flute item, there's a new item to wield in the form of the Mirror of Worlds... but that's all you're getting from me in terms of spoilers!
Head to the official project page for more information!