Search for the extended regex expanded by"$MONTH\/$YEAR.*GET.*ad=$ADVERTISER HTTP\/1" in the decompressed contents of the /var/log/apache2/access*.gz files that are newer than ./tmpoldfile and older than ./tmpnewfile
find /var/log/apache2/access*.gz -type f -newer ./tmpoldfile ! -newer ./tmpnewfile \ | xargs zcat | grep -E "$MONTH\/$YEAR.*GET.*ad=$ADVERTISER HTTP\/1" -c