kill two birds with one stone 一举两得；一石二鸟；一箭双雕

【例句】
After all, addressing the problem could kill two birds with one stone.
毕竟，解决了这个问题，可以收到一石二鸟之功。

We can kill two birds with one stone by dropping off the mail when we go to the grocery store.
我们可以在去杂货店时把邮件寄出去，这样就能一举两得。