What is ZIP?

The archive format both Windows and macOS open by double-clicking, which is most of why it won. Each file inside is compressed on its own, so you can pull one out without unpacking the rest - handy for browsing, slightly worse for compression ratio.

What is TGZ?

A tar bundle compressed with gzip - the standard Unix archive. Because gzip sees the whole bundle at once rather than each file separately, a folder of similar files compresses better than the ZIP equivalent. The catch is that reaching one file means decompressing everything before it.