Remember:
• for the [z] sound, the air and vibration should be at your front teeth, which gently press against each other;
• for the [ʒ] sound, the air and vibration should be at your side teeth, which gently press against each other.
• [z] – front teeth
• [ʒ] – side teeth
• [z] – front teeth
• [ʒ] – side teeth