Merging output of one document in next

I am working on a pipeline where I am reading data from CSV generator.

I have 2 types of data H line and I line for each one I need to do some mapping, which is fine. the final output I need to sent to SAP with a format H + I

So I need to merge the H line to each I line and then post to SAP.
Can someone help me achieve this? As all the values are in an independent document I am not able to do it easily. I tried Join and Union followed bu Group by but still not getting desired result.

Desired result:

/KS