Issue moving .zip file contents to external hard drive

I have some zip files whose contents I have been trying to move over to my seagate external hard drive. Every time I try to move the contents (not the actual zip file) over to the external it successfully copies them, yet afterwards when I delete the zip file and contents from the Mac's hard drive, both the copies of the files on the computer and the hard drive are deleted at the same time. I see no reason why it would ever do this seeing as the files on the external are completely new copies of the files on a different drive. Anyone else have this issue? It's incredibly annoying.

G'day and welcome to the forums.

Emptying the Trash does that. Move the files, check they are on the external, and then disconnect by dragging external drive icon to the Trash, or right clicking. After thee xternl is safely disconnected then empty the Trash on your Mac.