The most voted answers did not work for me on Windows 11. After a bit of fiddling and checking 7zip's command line options, I came up with this:

for /d %%X in (*) do ("C:\Program Files\7-Zip\7z.exe" a -tzip -r "%%X.zip" "%%X/*" )

Using this line in a batch file and executing said batch inside the desired main folder, all subfolders (with their respective contents) are zipped into individual zip files.