How to play 4,7 on Guzheng?

The guzheng belongs to the pentatonic scale, and there is no place for the 4 and 7 tones in its 21 strings. When there is a 4 or 7 note in a piece of music, you can only rely on your left hand to press the 3 or 6 strings on the left side of the zither to increase the tension. To play the 4th note, first press the 3rd string 15 to 20 centimeters away from the left side of the zither, and then play the string with your right hand to play the 4th note, and to play the 7th note, first press the 6th string with your left hand, and then play the 6th string with your right hand to play the 4th and 7th notes. When playing the 4 and 7 tones, you must pay attention to two points: i. The method of playing the 4 and 7 notes is significantly different from the upward sliding notes: for the upward sliding notes, the right hand plays first, and the left hand presses the strings to make the notes slide upward, while for the 4 and 7 notes, the left hand presses the strings first, and the right hand presses the strings later. And the speed of the left hand's string-pressing action is also different, the former action is more gentle, the latter action is more rapid. So when playing the 4 and 7 notes, you must avoid mixing them with the upper slide. II. The power used by the left hand when playing the 4 and 7 notes is not equal. Because pressing the 3rd string to the 4th string is a small second change, using less power, while pressing the 6th string to the 7th string is a large second change, using more power.