diff <(grep somestring file1) <(grep somestring file2)

:h

I use this one a lot too. If you put it after a filename, it will change that filename to remove everything up to the folder. Like this:

grep isthere /long/path/to/some/file/or/other.txt
cd !$:h

9. Startup Order
   https://blog.flowblok.id.au/2013-02/shell-startup-scripts.html