You can have 2 sheets .
Sheet 1 - having first 2 columns , column 1 to show selected Year data , Column 2 to show the December - yr (selected year)
Sheet 2 - having one column for selected month data
Bring these 2 sheets in the dashboard , make the second sheet floating on the other as if it is one single report.
Make the filter year applicable only to sheet 1
Make the filter month applicable only to sheet 2
This will fetch the data which you are expecting . Let me know if this helps.