I'm a decent programmer and I know my way around an image program, but the latter takes me much longer for tinier gains than the former. It's completely different for each person, but if you're doing the art yourself, that will still take up a notable amount of time.
Is the combat action-oriented, or turn-based? You mentioned both Zelda and FF so I wasn't quite sure. With one, you'll have to worry more about proper hit detection and the physics of movement and attacks, which can be a little troublesome. The other can be technically simpler (if you're not making the number system complicated,) but can be further improved with some flair to make it interesting to sit through.
And that's where you can cover yourself on the features - You can call out the concepts in general, but still allow yourself the room to dress it up a bit too.
Plenty of games have been made in 6 months or less, though usually with some level of experience - and drastically differing levels of quality. Comparable to your concept, "Cthulu Saves The World" was released 9 months after their previous title, but carried over a lot of the development work from it too. I don't know how long they spent on its predecessor, but this was in one interview about it:
Reyes: ... what would you say was the most difficult aspect of making your own role-playing game?
Boyd: Probably programming the battle system and related code. I went in thinking that I’d have the battle system code done in a week or so, and it ended up taking over a month to do.
I was thinking of making it technically more FF related with the battle system. The numbers system wouldn't be complicated or anything. Looking at Cthulu saves the world, it would be similar in concept to that game too. If that took experienced people 9 months, I don't think me on my own would come close to making a finished game, perhaps a couple of levels...