Make a multiple Select Statement with union ALL clause

Hello there,
I have this query

SELECT created_datetime from rtv_spare_parts_repair_header where approved is not null
UNION ALL
SELECT created_datetime from rtv_spare_sp_requisition_header where approved is not null
UNION ALL

it is working.

now I want this to divide this into two SELECT statement with UNION ALL

How can I do that?

I cannot search it on google I just ask it here

all answers are appreciated