..Really? Her SH N-air wouldn't even hit DK or something? Hm.. It's been awhile since I've played, but I figured someone might get hit if they were the tallest, or close to it, of the game.. Ehh.
Her U-air is still good you know, she gets a few combos out of it, and combo or not she can often land two in a row on low damage %s, especially if they're heavy character.
At the same time, her ground game is all she really has to play by.. Her aerials rarely can be used off the bat as a quick approach or even defense/spacing, bar a few exceptions.
Zamus has a lot more options than a B-air kill, you know. Her F-air certainly has the power, and once you get used to using it it's very easy to land the second hit, I've seen tons of Zamus mainers land a kill with it. Her Side B is obviously a good kill if you're not spamming it, since it has both the range and power.
While it is hard to land spikes with her Up B and Down B, they're also possible. Stunning the enemy below a lipped stage(FD, Smashvile, etc.)with a D-smash then B-airing them to a stage spiked doom is a wonderful kill as well, although rare. Stages with low cielings(Corneria)make it possible to get a star KO with U-air as well.
Also, about her D-air.. It certainly isn't the best move, but it can come in handy. If you need a quick interupt or to suprise an enemy, you can use it, just very sparringly. I'm saying it's not a bad move, although it's not a good one either.. Average, really.