The sentence asserts the arrival of both men. It gives us the joint fact of arrival, but not the exact times.
«جاء زيد وعمرو»
Zayd and Amr came.
Three scenarios remain possible:
1. Zayd arrived first.
2. Amr arrived first.
3. They arrived together.
Waw by itself selects none of these.
Where legal consequences depend on chronological priority, an additional textual or contextual indicator is therefore needed.