زَيْدٌ مُنْطَلِقٌ وَعَمْرٌو
Zayd is departing, and ʿAmr too.
In the first clause, «زَيْدٌ» is the subject and «مُنْطَلِقٌ» the predicate. In the second, «عَمْرٌو» is a nominative subject whose predicate is understood from the first clause. Its reconstruction is زَيْدٌ مُنْطَلِقٌ وَعَمْرٌو مُنْطَلِقٌ.
If the first predicate were «جَالِسٌ», sitting rather than departing would be inferred for ʿAmr. The name ʿAmr itself supplies no such meaning: the preceding predication provides the clue.
The omission prevents needless repetition when the intended judgment is clear. If the occasion requires an individually emphatic assertion about each man, stating both predicates can serve a different rhetorical purpose.