To see your transaction history on ZMZ, select the "Transactions" option from the top of the page.
You'll see a list of all of your previous transactions, sorted by project name. On the far right side of each of these list items, you'll see a blue text that reads "Download Invoice." Click there to see the basic information about this transaction.
To download, click the yellow "Download" button at the bottom of the screen. You can also print the invoice by pressing the "Print" button next to it.