SQL & PL/SQL

Hi I have an issue When I execute my procedure I have this error
ORA-00933: SQL command not properly ended. But I tried to print the same sql statement and execute and it gives the output.. could some body please help here is my sql script

EXECUTE IMMEDIATE 'SELECT ' ||house_master ||'.addr_zip_5 FROM ' ||
customer_master || ' , ' || house_master || ' , ' || equipment || 'WHERE '|| customer_master || '.site_id='|| house_master || '.site_id AND ' ||
customer_master || '.account_number = ' || equipment || '.account_number AND '||
equipment || '.house_number =' || house_master ||'.house_number AND ' ||
customer_master || '.account_number = ' || accountNumber || ' AND '|| customer_master || '.site_id = ' || siteId INTO zipCode;

could somebody please help me

thanks..