How to merge two sitemaps

Hey there,

I have a blog at https://www.jeremydavid.com, and I just moved all of my files to https://www.jeremydavid.com/old.

Is there a way that I can merge the two site maps together? I use your plugin on both pages, but I would like to have one sitemap for https://www.jermeydavid.com that includes all of the posts there, but also the ones from https://www.jeremydavid.com/old.

Cheers,