Here's one example: Golden Axe Warrior for the Sega Master System. See if you find any similarities with Zelda.
Zelda II: The Adventure of Link, considered the "Black Sheep" of the series, also has its copycats. The following is an episode of the Angry Video Game Nerd presenting Rambo for the NES. See if you can spot any similarities in that game with Zelda II.
In future articles I will present more Zelda clones. Let's see which ones are worth trying.