If each attachment is different there is not an option to bulk send the email based on this.
I would highly recommend you to please post this idea at our ideas forum (here).
Our product team, who monitors the forum regularly, can read your specific use case and understand why this would be a useful functionality or change. It also helps other customers facing the same issue to advocate for its implementation on your behalf by upvoting on the thread as well.
If the attachment is the same but you would like to send separated to each of the users, you can send a sequence ( more information here)