Fireball zoning doesn't seem AS strong in this game as Capcom games. As bigvador said with King, mix hers up. Try to do read fireballs i.e. full jump backwards, do one at the top of your jump while they may be expecting one low to the ground. At lot of players here surprisingly get hit by that one the most because they expect one shooting AT them.
Also, on the reverse, you wanna shoot fireballs based on YOUR outcome. Like if you expect someone to jump, do the B version, so you recover faster and hit them with a far s.D to keep them out. Alternatively, if someone is rushing you down, do the airborne D version, so you fly backwards and force the opponent to guess through few fireballs.
Of course, if they get through two, maybe one if close enough, you're in for a world of hurt. Just play carefully, see what your opponent likes to do in response to fireballs and read it. Versus just trying to throw them out and zone. Pretty much reverse of Capcom style games, I suppose