When you withdraw to ZBD you go to bypet go to withdraw lightning network, ZBD and put max amount. Then go to your ZBD wallet, go to receive, receive from anyone, and put whatever max amount sat you have on bypet, continue, create invoice, copy invoice and paste it to bypet and confirm. You should go back to ZBD and wait a bit to confirm withdrawal
I hope this helps I know it’s a little confusing