Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_25679 ( "Stage" real, "Winner" text, "General classification" text, "Mountains classification" text, "Points classification" text, "Youth classification" text, "Team Classification" text )

### Question ###
Who was Mountains Classification in the race with Nick Frey as Youth Classification and Tom Zirbel as Points Classification?

### Accurate SQL ###

SELECT "Mountains classification" FROM table_25679 WHERE "Youth classification" = 'Nick Frey' AND "Points classification" = 'Tom Zirbel'