Starting from V2.6.4, it is allowed to gift an item when ordering. But you have to give permission for the item in advance. If not yet, please click the link to check:
How to Make an Item Available as a Gift Item – Zii Help Center (ziicloud.com)
Tap the item after it is chosen when ordering.
Toggle on “Gift” and click on OK.
Then you can see the price of this item turning to “0”, which means it is a gift item now.