The Shiyijia zhu text reads zheng 政, "governor" for zheng 正, "measure." (For background on this translation of zheng, see Wu Jiulong, p. 61, which cites comparable phrases from the Guanzi and Laozi.)
Here dao stands alone as, simply, "the way." In the many other references to dao in the Sunzi we find the term always qualified as "the way [of something]," for example as guidao (the dao of deception, chapter 1) or "zhisheng zhi dao," "the dao of knowing victory" (chapter 3). Even when chapter 1 lists dao standing alone as one of five qualities (the others being heaven-earth-humanity and method, as here), it soon supplies a definition: "Dao is what causes the people to have the same purpose as their superior."
The present passage is therefore open to many interpretations. The linkage to fa, "method," encourages us to read it in the context of chapter 1--but the subsequent passage treats fa very differently from chapter 1. Furthermore, the combination of dao with xiu, "cultivate," puts the term much closer to the so-called philosophical of the Masters (zi) texts of Warring States times.