Letter Dhaal is pronounced with tip of the tongue touching bottom edges of upper two front teeth (incisors) There should be enough protrusion of the tip tongue
Letter Daad is pronounced when up turned side or sides of the tongue touches the upper back teeth (pre-molars)
Letter Zaa is pronounced with tip of the tongue touching the edge of the lower two front teeth and lightly touching the upper two front teeth as well . it will produce whistling sound