Network fees are paid to the blockchain network operators (miners) who confirm all transactions on the blockchain. Network fees change over time based on network conditions and are not paid to Zengo.
To find out how much fees you would possibly pay for a transaction before making the transaction follow those simple steps:
start the transaction you want to make (any amount) on Zengo
after selecting the amount and entering the destination address, press "continue"
A summary page will present your transaction details before the confirmation.
The network fee will show there.
You can also check this page to find out more about the average Ethereum and Bitcoin network fee (which may vary and change over time)
Note: on Bitcoin and Ethereum, you can reduce the network fee by choosing a different Transaction speed.