The Gemora cites a braisa: There is greater stringency in oaths than in vows, and greater stringency in vows than in oaths. There is greater stringency in vows, for vows apply to objects necessary for the performance of a mitzvah just as to optional matters, which is not so regarding oaths (which do not take effect if one would take an oath against performing a certain mitzvah).  And there is greater stringency in oaths, for oaths are valid with respect to matters that have substance and matters that are intangible, which is not so regarding vows (which do not take effect on intangible thing).

It is noteworthy that the Zohar writes exactly the opposite. An oath, he says, can only take effect on a davar she’yeish bo mamash, something that has substance, whereas a vow can take effect even on a matter that lacks substance.

The Shoel U’meishiv in his haskamah to the sefer Beis Yisroel cites from the Neizer Yisroel that it is a printer’s mistake and the correct version of the Zohar is the way the Gemora states.

Reb Reuven Margoliyos disagrees and cites a Ramban in Shavuos who hints to the version that we have in the Zohar. The Ramban writes that according to Sod, vows take effect only on matters with substance, whereas an oath can be effective even on matters that lack substance.

In the sefer Mei Hashiloach, he explains the Zohar in a manner that is identical to our Gemora. We find in the Zohar that a davar she’yeish bo mamash frequently means something that has the ability to reproduce. The reason that an oath can take effect even on intangible matters is because an oath is an issur gavra, one is prohibiting himself from the object. The oath, therefore, is taking effect upon the person. The meaning of the Zohar is that an oath takes effect on the person, for he is a davar she’yeish bo mamash, i.e. man has the ability to reproduce; objects do not! An oath takes effect upon the person and not on the object. A vow, on the other hand, takes effect even on a davar she’ein bo mamash, something that does not have the ability to reproduce, i.e. objects. For by a vow, one is prohibiting the object upon himself (issur cheftza), and therefore, the vow takes effect upon the object, not upon the person.