If the funds on a given account are insufficient to complete the transaction, the missing part will be automatically debited from EUR, USD, GBP, or PLN accounts and automatically converted at no cost. All you have to do for the automatic conversion to work is to have funds in your EUR, USD, GBP, or PLN accounts. ZEN will check the EUR account first, then USD, then GBP, and finally PLN and take the funds from the account where there are enough funds.
Anna wants to pay for purchases in PLN. However, she does not have a sufficient amount on this account. The missing funds will be converted automatically. ZEN will check the EUR account first, then the USD account, then the GBP account and take the funds from those accounts one by one to ensure that there is enough money to cover the transaction.
Charles does shopping on eBay. He wants to pay in USD, but there are no funds on his account in this currency. ZEN will automatically convert his funds by checking his EUR account first, then GBP, and then PLN. Funds will be withdrawn from those accounts where there are enough of them.