There are only a few passed on from ancient times. Zheng and Qin resemble in looks, but in fact they are completely different. Qin has seven strings, while Zheng has unfixed number of strings.

筝的外形看起来和琴有几分相似， 实际上完全不同， 琴有七根弦， 而筝弦的数目却并不固定， 但通常是十三根弦， 并且所有弦都有音柱支撑。

youdao

Down here, Liu Qin-Zheng practises his art with no hurry and clear enjoyment.

BBC: Here be dragons