جَاءَ زَيْدٌ وَهُوَ يَضْحَكُ.
Zayd arrived while laughing.
The pronoun 'huwa' refers to Zayd, and the nominal clause describes his concurrent state. The presence of wāw does not automatically make the construction coordination of two independent reports.
«جَاءَ زَيْدٌ يَضْحَكُ» can likewise express a circumstantial state, now with an affirmative imperfect unintroduced by wāw. The surface forms differ while the core relation remains similar.