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_19834 ( "Stage" real, "Winner" text, "General classification" text, "Points classification" text, "Mountains classification" text, "Combination classification" text, "Team classification" text )

### Question ###
If winner is alejandro Valverde and the points Classification is by Erik Zabel, who is the mountain classification?

### Accurate SQL ###

SELECT "Mountains classification" FROM table_19834 WHERE "Winner" = 'Alejandro Valverde' AND "Points classification" = 'Erik Zabel'