Cron Job for everyday except second Sunday and fourth sunday

Although I think it's a bad idea and it would be better to run it every 14 days, this should do what you want. (To run at 4:00 at night)

0 4 1-7   * *    test $(date +%u) -eq 7 && ./yourscript.sh
0 4 15-21 * *    test $(date +%u) -eq 7 && ./yourscript.sh
0 4 22-31 * *    test $(date +%u) -eq 7 && ./yourscript.sh

Edit: I forgot to add minutes -> fixed