Ex2 Ultra - Best way to Compress older folders? - Please suggest

My Cloud EX2 Ultra - -Some of the folders may range >5 GB in size including sub-folders.
My 2 TB Red (mirrored) drive is reaching 1 TB in use. Over 80% of the Folders are > 5 years old.
Even at the expense of it taking time to search for them, I would like to compress some of them.
Four Windows 10 PC are networked to this EX2 Ultra.
Do I need to add an App to the EX2?
What advice to select folders and Compact (or compress) them would users suggest?

ZJP the folders so you can compress them yet easily see their contents.

So just a regular Zip works.
Thanks -