Derived column syntax help needed

I am struggling getting the following case statement into the derived column format in SSIS




CASE 
WHEN SUBSTRING(REPLICATE('0', 9 - LEN(Data)) + CAST(Data AS VARCHAR(9)), 4, 6) IS NULL
THEN 0
ELSE RTRIM(SUBSTRING(REPLICATE('0', 9 - LEN(Data)) + CAST(Data AS VARCHAR(9)), 4, 6))
END

Here are examples for the data in Data
row 1 - 1201303
row 2 - 123456789
row 3 - null
row 4 - 12345678
the first row result would be 201303
row 2 result would be 456789
row 3 result would be 0
row 4 result would be 345678

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Andre Toerien