2.1.426 Part 1 Section, zoom (Magnification Setting)

a.   The standard states that the percent attribute is required.

Word does not always require this attribute.

b.   The standard specifies that a percent attribute value of less than the minimum zoom level shall result in display of the document using the application's minimum zoom level.

Word treats this attribute as omitted when it has a value of 0.

c.   The standard states that this element specifies the magnification level which should be applied to a document when it is displayed by an application.

Word 2013 ignores this element when reading a document.