Just like the previous trips, Zhang Zian would try to pick the night flight when he came back, mainly to save some social trouble. If he came back when the store was open, he would inevitably have to face the staff and old customers 'questions, especially about where the unique pets in the store had gone and why they didn't come back with him.
He could make up an excuse to explain, but why did he have to use his brain? It was better to come back at night and take a nap to relieve the fatigue of the trip. The next day, without his explanation, people would take it for granted that he had brought the elves back with him.