Apple - How to search for .zip files instead of all compressed files?

Open a new finder window and type "zip" in the search. Select "Zip archive" in "kinds".

You can also just type out kind:.zip and press enter and you'll get the appropriate filter:

Note - omitting the . after the : results in many compressed files and not just those with .zip extension or literal conformance to that specification.

Type ⌘+F on Finder and you will see the search bar. By default appears Kind is Any. Replace Kind with File Extension (you can find it under Others...), then you can type zip in the field and you will have the results immediately.

Additionally if you feel confortable with the Terminal, you can use the following command:

find . -name "*.zip"

You can directly search for zip files by entering:

kMDItemFSName:.zip

or even better:

kMDItemKind:"Zip"

into Spotlight Search in Finder.

To get more kMD* keywords make mdls /path/to/file in Terminal to list them.

Here is great pdf with a list of search attributes and other hints.