It is a combination of proper technique, proper breathing and timing. And this can only be learned through constant repetitive practice. Once your body gets used to the movement and you learn to relax, you should be able to explode into action and perform the kata in a whiplike motion which causes your Gi to make those snapping sounds. Because without proper technique, you won't be able to create those sounds.

You quit doing kata and do some real training...

I'm an Ed Parker American Kenpo practitioner at brown belt. When I do katas like short and long firms to get a bit of flash/ snap power I practice a lot for fluidity and my go has a nice snap. To it. Other than that it's getting down fluidity and giving it your all

It is because of the gi that you hear those sounds. Ask your instructor that is seeing what you are doing to aid you in that.

Practice again and again with ease of breath.

"Zip" the punches and kicks, but with precise timing.

I always see that when people do their kata, we hearing their movements and 'breathing'(for e.g when they do a gedan barai or shuto uke) . How can I do like that?

Is it because of their strength or kimono quality or something else? This makes them appear really wow. That's what was always lacking..

I really want to improve my kata. Help me out please!