Zil 4421 for ETS2 1.36 DX11

Zil 4421 is 5423's older brother. This is the real Zil 4421, no fake outdated files, no 750HP engine, no fancy tuning hassle, just Zil 4421.

- ETS2 1.36 DX11 update
- Motor rewrite closer to reality
- Air cables added
- Added to Zil custom dealership
- Log file almost clean