All of the above answers are excellent, but do not tell the whole story (neither will my input!) but for example NEVER try zipping files that are not compressible, that is a lot of graphic formats and almost all video formats and of course files that are already in a zip (or other similar compressed) format......
Trying to compress files that are un-compressible usually just makes them bigger as well as putting a huge load on your CPU for no reason.
Sadly a lot of compression algorithms do not tell you up front what is not compressible or that the resulting file is either the same size or bigger.......and software authors are very sensitive to being told that their baby is ugly......
You would be surprised how normally intelligent people just do not understand what I have written here, in my last job I spent a lot of time trying to train customers on how to use compression correctly.....some just NEVER understood it.....
Remember also that there are basically two forms of compression - lossless and lossy....
.jpg files actually lose some of the data of the picture each time the picture is saved in the .jpg format (there are sometimes ways to turn it off in some software packages!) whereas generally speaking, computer data must be returned to its original exact size and number of bits each time it is un-compressed!!
Different algorithms work better on different data, a good compression program adapts itself to the type of data that needs compressing, some are clever enough just to re-save the data with a new extension instead of actually trying to compress it !
The user then thinks that the program is wonderfully fast!!!!!
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"What others say about you reveals more about them, than it does you." Anon.
Winzip is always behind other Archivers/ Splitters / Extractors.
Especiaaly in the time of "Mounted-Drive" era & still is behind of many.
eg:
QUTILITY.EXE is a free Zipping/ Splitting program of the Win95 era. Astonishingly works with WinXP. It offered SPLITTING of files to any size or Standard-Floppy size on floppy or copy to HDD with progressive number to be copy to Portable ; when Winzip was still "Spanning" to floppies 1 after the other with the common file-Name [you cannot copy in the same folder].
And if any of the floppie(s) go bad [as the most un-reliable Media-of-the-day] you have to do all the drill afresh. [Floppies were not as bad then as today]
Leave aside a huge number of Free SW in Archiving, fully functional & recognized by all ZIP
SWs: 7zip, freezip, bcarchive.exe, bxautozip_v*.exe, info-zip.exe, ShellZip.exe, superzip.exe, szip.exe, TUGZIP*.EXE, wlh*.zip, zcsetup.exe, zg*std.exe, zipit*.exe, zipzag.exe, ALZip63.exe, IZArcCL.exe, powerarc611.exe, spinzip-setup.exe, zg603sui.exe
and a lot more ...