と同時に
文法の解説は英語です。
用法
と同時に means that something takes place at the same time as other actions or events, or that something is the case while something else also the case. "As soon as; the moment; at the same time; also; as well"
例文
電車のドアが開くと同時に、多くの人が降りて来た。
When the door of the train opens at the same time a lot of people get off.
新しいゲームソフトは発売されると同時に、全部売れてしまった。
At the same time as that new software game was put on sale, everything else was sold.