Cannot seem to get my loops right

I have a search result of customers and items and serials

I have a custom transaction that I would like to create based on this search result

For every change in customer I want to create a new transaction  but how do I get into the loop to create the sublist of items

I thought I could loop through the customers and push into an array the items needed for the sublist and then create the record and put in the items but,

How do I get back to the top of the first loop and keep moving to the next customer.  I can’t figure that part out.