A .zip file of this name typically contains the full standalone game directory for the Windows platform.
The version number "1.5.x" signifies a significant engine transition for the game: File: Hollow.Knight.v1.5.75.11827.zip ...
This branch introduced 64-bit support, improved controller compatibility, and fixed several long-standing physics bugs, such as "super-dashing" issues. File Characteristics improved controller compatibility
This report provides details on the specific build version 1.5.75.11827 , which was released in June 2021 as part of the game's major v1.5 update. Patch Overview: v1.5.75.11827 and fixed several long-standing physics bugs