While means "When ... uses the progressive verb, it is unnecessary to use the ing form. But sometimes when you are not a progressive verb, you have to use while, so you change this non-progressive verb into a progressive verb. The ing form of the verb "Zheng ……" can semantically lengthen a short action, so when while is followed by a discontinuous verb, the progressive tense is used.

While means "and" leading adverbial clauses, and there is no need to use progressive tense.