Hi @copycareoffice 

I'm almost certain you could do this a few years ago via Import Invoices using a csv file.  It's a long time since I've used it but the mapping options for Custom1/2/3 now seem to have disappeared.  It must be one of those customer-requested improvements to QBO!

If the imports are of past invoices - i.e. just for reference - you could edit your csv file(s) to merge the custom fields into one & map that to <Memo> (assuming you're not already using the memo field, that is).

Alternatively, as you're already using Zed Axis to export from QBD their Zed Axis Online might be your best option for importing that data into QBO.

Hope this helps.