Download multiple files simultaneously (parallel) with custom filenames
Aria2c supports getting URIs from a file.
Try writing your file names into the file and then running "aria2c -i uri-list.txt" or write them to stdout and pipe them to "aria2c -i -"
with -Z option:
-Z, --force-sequential[=true|false] Fetch URIs in the command-line sequentially and download each URI in a separate session, like the usual command-line download utilities.
so in your case:
aria2c -Z URL1 URL2 URL3 URL4