Can I be hacked during transactions?

No. As your private keys are never exposed, they - and therefore your crypto - cannot be stolen.

There is one important step though: when you scan the transaction request QR code from the app with your ZERO, your ZERO will show you what you are about to sign. Here you need to verify that all the transaction information is the same as on your app. If that is the case, you can sign the transaction, and that's it!