The nearest airports are: Poznan (140 km), Wroclaw (150 km), Berlin in Germany (200 km). Poznan and Wroclaw are connected with Zielona Gora by railway: (http://rozklad-pkp.pl/en). Berlin is connected by Flixbus: https://global.flixbus.com/bus/berlin
There is also an airport in Zielona Gora (Babimost) which offers a connection with Warsaw. http://airport.lubuskie.pl/
Note: Due to "Winobranie-2019" Polish Wine Festival in Zielona Gora which will take place during the days of Conference CGE-2019, please make hotel reservation in advance.