Ultimacraft HD (alpha).zip is an alpha file of the Minecraft resource pack UltimaCraft HR, made for Minecraft 1.16.1, 1.15.2. It was published on July 21, 2020 and is 201.3 MB in size. Pre-release builds can contain bugs — back up your world before installing. For the full description, screenshots and every other version, visit the UltimaCraft HR resource pack page.
How to install: Put the .zip into .minecraft/resourcepacks (do not extract it) and enable it under Options → Resource Packs.