Angelfish are not hard to keep at all,
unless your nitrate is sky-high, pH is totally out of range, and you have ammonia and nitrite present in your water ... heh

But if you're familiar with the cycle, you probably have water good enough for angelfish

Besides, they can be kept in a community tank, only it's best to have 2 angels per one tank, so that in case they are a mated pair, they won't bully any other fish in the tank that are of similar size to the angels. My angels breed all the time and they don't mind my neons at all.
Anyway, a 10 gallon tank is too small for angelfish (I'd recommend at least a 30 gallon tank for angels). But there are many other small and beautiful fish species good for a 10 gallon tank

Six neon tetras would be very good for a 10 gallon tank. I don't know much about guppies, but if they're not schooling/shoaling species, 3 guppies would be OK as well. So, I think adding 5 - 6 neons, or 3 guppies, to a 10 gallon tank with 3 zebra danios and 1 cory, would be OK. By the way, how large is the cory?