user: Question: what is the name of the constructor that has the circuit Zeltweg Airfield?
Columns: ['Race Name', 'Circuit', 'Date', 'Winning driver', 'Constructor', 'Report']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['II Lombank Trophy', 'Snetterton', '26 March', 'Jack Brabham', 'Cooper - Climax', 'Report']
SQL:

assistant: SELECT "Constructor" FROM "Table" WHERE "Circuit" = 'Zeltweg Airfield';