Xing, ziran are both commonly translated into English as nature, but the two terms have no semantic relationship to each other in Chinese. The translation nature has implications (English terms such as laws of nature, mother nature, and so on) from Western conceptual scheme of a transcendent reality that was nonexistent in ancient China. In ancient Chinese thoughts, there is a concept of an order that we may call natural. However, in the contexts of this natural, the earth di 地 is spoken of as mother in a dual relationship with sky or heaven tian 天, which plays the role of father. There is no concept of nature as a distinct entity that may act in accordance with law or that may be called mother.
Xing is conventionally interpreted as human nature, which refers to Confucius' saying men are close in nature but far apart in practice, (The Analects, SZ, 2524) The focus here is wholly on making oneself good rather on the ontological discussions of the original nature. Benjamin Schwartz remarks that this moral pragmatism or existentialism does not preclude a stress on inwardness. (Schwartz, 177) The recent scholarship recognizes that xing is inborn or innate qualities man or a plant is endowed with at birth, and it is a dynamic, not a static term. (Allan, 108) From Confucian viewpoint, this inborn or innate nature can be cultivated, if the first shoots of a plant or human mind/heart are nurtured and allowed to develop into full maturity.
A. C. Graham contends that the first reliable recorded usage of xing is found in statements describing the doctrine of Yang Zhu 揚朱, which does not simply refer to innate natural propensities in general but to the particular propensity of human beings to pursue their own natural desires for health, long life, and freedom from anxiety. (Schwartz, 175) On the other hand, in Zuozhuan 左傳, it assumes how the question of human nature can be related to questions concerning the Way of Heaven. It correlates all sorts of natural phenomena to human phenomena in numerical categories, or the correlative cosmology of the Warring States Period.
Ziran is commonly translated as spontaneous or spontaneity, nature or natural. Zi means self, ran is a general verb meaning be so, or it is so, thus, following A. C. Graham, ziran may be translated as to be so of oneself. On the contrary, the Taoists do not cultivate the inborn nature, or mind/heart, nor hack it away. Zhuangzi advises us, Let your heart/mind roam in the flavorless, blend your breath (qi) with the featureless and accord with the manner in which living things are so of themselves, not leaving room for self interest, and all under heaven will be in order. (Guo, 294)
References:
Allan, Sarah. 1997. The Way of Water and Sprouts of Virtue. Albany: State University of New York Press.
Guo, Qingpan 郭慶藩. 1997. A Elucidation on Zhuangzi, Zhuangzi Jishi
莊子集釋. Beijing: Zhonghua Shuju.
Schwartz, Benjamin I. 1985. The World of Thought in Ancient China. Cambridge, MA: Harvard University Press.
SZ. Commentaries on the Thirteen Classics, Shisanjing Zhushu
十三經註疏.1979. Beijing: Zhonghua Shuju.