The firebender raised an eyebrow at her attempt, finding it a good mimic, but not quite something that would do her any good. He backed away from her and went to grab the other blade, moving to now stand before her. Tilting his head, he bit his lip as he let the thoughts in his head process enough to be turned into words that wouldn't insult her. It took him a while, but he'd learned to think before opening his mouth, as his words tended to get him in to trouble. His previous spats with Katara were evidence enough.
"Good, but don't try to mimic the movements perfectly so much. Rather, try and...translate them into something that better suits you."
Realizing how confusing that must sound, Zuko tossed the blade up and caught it in his right hand, spinning around as he let the blade dangle menacingly before him, dropping to one knee when he came to face her again, jutting the tip of the blade to the side underneath a chambered arm held close to his face. He raised back to his feet.
"I'm taller than you, so when fighting with a weapon such as a sword--" he gave the blade a twirl for show "--I tend to aim high; chest, arms, and sometimes abdomen. You, however, would be better to aim at the lower half of the body. So, when doing what I just showed you--" he swung his own blade down and to the left "--start the movement a little lower, not so high as before."