Amazon often combines separate orders for shipping so this approach wouldn't work unless you waited for the first order to ship before placing the second.
I've always hoped they would do this but haven't been able to get them to even when I try. Like, going out of my way to select "Amazon day delivery" nearly a week out, and separate orders within a day of each other still come separately or even on different days.
I'm sure it just comes down to what's available in what distribution centers, how big the order backlog is, Prime status, etc. The algorithm that makes those decisions would be fascinating to study.
