You only need to download MHFZ_Overlay-win-Setup.exe, and run as Administrator.
Updating from v0.35 and older requires a fresh install.
SHA256
MHFZ_Overlay-win-Setup.exe 2379733A03C2E7AEAE9543C00BAAB1BF9A08063F22F5ED1F5C4A46C1257892AC
MHFZ_Overlay.exe C8DD3F7ED3EB52CB2D3067980D87981C7F1B2BE62F48BD778E60855ECAB42CA1