OLD_NS=7.7.7.7
NEW_NS=8.8.8.8

for TYPE in A CNAME MX TXT; do
    for i in $(cat /tmp/example.com.inc | grep ${TYPE} | cut  -f1); do
        OLD=$(dig @${OLD_NS} +short ${TYPE} ${i}.example.com)
        NEW=$(dig @${NEW_NS} +short ${TYPE} ${i}.example.com)

        if [ "${NEW}" != "${OLD}" ]; then
            echo ${TYPE} ${i}
            echo OLD: ${OLD}
            echo NEW: ${NEW}
            echo
        fi
    done
done