。。
It's all over. There's nothing more we can do.
Literal
All-things have-ceased [copula-だ]. Already do-nothing-can-do.
万事休す is a literary 四字熟語 ('four-character idiom') meaning 'all is over,' 'all hope is lost.' 休す is the classical form of 休する ('to rest, to stop'). The second sentence どうしようもない (literally 'there's no way to do anything') reinforces the despair. Classic dramatic defeat pattern.