Database: european_football_2
Question: State the chance creation passing class for "PEC Zwolle" on 2013/9/20.
SQL: SELECT t2.chanceCreationPassingClass FROM Team AS t1 INNER JOIN Team_Attributes AS t2 ON t1.team_api_id = t2.team_api_id WHERE t1.team_long_name = 'PEC Zwolle' AND SUBSTR(t2.`date`, 1, 10) = '2013-09-20'