IFWiki: Fweep
Fweep 0.8.4, a Z-machine interpreter in portable C, supporting all Z-machine versions except 6. Does not require any special terminal mode or similar, therefore many features (such as the upper window) are unavailable. Also includes a debugger. Archive includes source code and a Windows console mode executable.
Zym 0.9, a Z-machine interpreter for SymbOS, supporting Z-code versions 3, 4, 5 and 8, written by Daniel Gaskell. Based on Fweep 0.8.4 but with many optimizations and changes, including upper window and diacritic support. Archive includes source code, SymbOS executable and story files.