Protocols that are used between Zabbix components are UTF-8 based. However for Windows version of zabbix_get, zabbix_sender no conversion to UTF-8 is done for the command line parameters.
For example, one can query Windows agent from Unix with the following command.
Equivavlent command doesn't work either from PowerShell or cmd.exe.
We should check how to solve this. One of the possibilities is to change main() to wmain() and then convert arguments from UTF-16 to UTF-8.