وَفِي اللَّفْظِ مُطَابِقٌ لَهُ
And in form it agrees with that subject.
A singular masculine subject such as Zayd normally corresponds to «huwa»; feminine or plural subjects require appropriately matching forms. Agreement in gender and number signals the relation to the previous subject.
الطَّالِبَةُ هِيَ النَّاجِحَةُ
The female student is the one who succeeds.
This additional example illustrates the principle of agreement without claiming to be the textbook’s original example.