[SQL] DB2 Usage of two combined fields in 'IN' operator

I want to write a sql with in operator over two fields, but this ending in a sql error

[Code: -811, SQL State: 21000] The result of a scalar fullselect, SELECT INTO statement, or VALUES INTO statement is more than one row.. SQLCODE=-811, SQLSTATE=21000, DRIVER=4.28.11


My sql condition looks like

AND
(
SELECT car.id1
FROM SYSIBM.SYSDUMM1
UNION ALL
SELECT car.id2
FROM SYSIBM.SYSDUMM1)
IN
(SELECT inn_car.id
FROM....
)

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