The primary differences in this version are: somewhat changed overworld, some changed monster graphics, and moved-around and added monsters in dungeons.

There’s a couple of cheap hits (especially a hammer throwing monster placed before a lava pit), and it requires some trial-and-error to find the tunnel to Palace 3 (it’s in the same place but it’s harder to find as it’s not as obvious where King’s Tomb is), but overall the difficulty is only slightly harder than the original game. You get harder enemies sooner, but you get more experience for them, so you gain levels faster. Experienced players will clean up, but players who haven’t beaten Zelda II a dozen times before will probably have a tougher time. But then, plain Zelda II is a pretty tough game itself.

Ultimate verdict: recommended, but only slightly. It’s not really changed that much, substantively, from the original.