"Search between a Pool, Windmill, and an Umbrella (Hard)" is one of the possible Daily Challenges in Fortnite Battle Royale.
Walkthrough
There is a group of 3 trees, near a wooden tower, west of Anarchy Acres (and north of a umbrella shaped excavation)
Solution: Search those trees for a Battlestar Item. The Battlestar Item is generally at the easternmost tree amongst those three trees.
Collect the Battlestar.
Map
The location is west of Anarchy Acres, marked with the red circle:
