How to pronounce [z]:
Lengthen your mouth, spread your tongue companied with pressing the tip of your tongue against the upper alveolar ridge and then loosen the tongue-tip a little to let the airflow out without vibration of the vocal cord. The sound of [z] is like the “z” in the English word “buzz”.
How to pronounce [c]:
The position of articulation is the same as that of [z] but you should blow the air out strongly. The sound of [c] is similar to the “ts” in the English word “sits”.
How to pronounce [s]:
Let the tip of your tongue contact the back of lower teeth, raise the mid-part of your tongue to form a small interstice with the upper teeth and then squeeze the airflow out through it.
The sound of [s] is similar to the “s” in English word “see”.
1. Vocal cord: [z] [c] [s] are all voiceless initials.
2. Articulation: [z] [z] [s] are all frontal-alveolar affricate.