جَاءَ زَيْدٌ وَهُوَ مُسْرِعٌ.
Zayd arrived while he was hurrying.
The wāw in وَهُوَ مُسْرِعٌ functions as a circumstantial connector, not simply as a conjunction joining two independent reports. The phrase describes Zayd's condition when the arrival occurred.
The pronoun هو refers back to the subject of the circumstance. Although the embedded construction is nominal, its discourse function is circumstantial, qualifying the event rather than offering an unrelated assertion.