First, get 7zip Command Line here.

Next, unzip to your desired directory – mine is in C:7za920.

Based on my previous post, MySQL: Backup Database using Batch File. Add the following lines after echo Database Backups Completed and before pause.

 
cd C:7za920
7za a myapp_db_%datestr%.zip D:BACKUPSmyapp_%datestr%.sql >Log.txt 2>&1
echo Zipping Backups Completed

Now you are done! Execute the batch file to see the result!

p/s: >Log.txt 2>&1 used for creating a log file for all the process to zip the file.