From the Closed World to the Infinite Universe by French philosopher Alexander Koyre.[Photo provided to China Daily]

And often, his favorite tunes by the German composer Bach play in the background.

Speaking of his work, he says: "I figured it out a long time ago that translation is the most important thing for me."

Zhang says his translation career took off accidentally in 2001, when he was auditing the class of Wu Guosheng, a science historian at Peking University.

Then, Wu asked him to translate a part of the book Newtonian Studies by French philosopher Alexander Koyre.

Wu was satisfied with his work and gave Zhang the job to translate the whole book.

Zhang spent the whole summer vacation on it.

Every morning, Zhang, who returned to his hometown in Henan province, took along the book, a dictionary, some paper and his lunch, to his family's new but empty house to work. And he wouldn't return home until dinner time.

With no computer, Zhang had to write out the translation, and type and proofread every word on a borrowed computer later, he says.

"The book was boring. But translation was fresh to me," he says.

His passion for translation didn't die.