We don't need more than one specialist spinners. Because we have Shakib for any type of matches. Ryad also effective in all types but he isn't used enough in Test matches. He even got five wickets in a Test match innings against West Indies at his debut in 2009. Nasir also joined the team as a alrounder and effective as well. Ashraful's leg spin can give break through. So only one can be selected from Razzak or Sunny.
On te other hand Ziaur can support the pacers with his medium. And only one pacer should be taken as a partner of Mashrafi.
Think a lot, speak a little.