I don’t have a ferret, so I couldn’t say for sure, but I would do it S L O W L Y. Especially since your one bun seems to get angry at the sight of the ferret. The anger may be more jealousy/territorial though. Go to a neutral place for both, like a bathroom that they aren’t normally in. It would help to have a second person on hand to help watch and break up fights if anything starts. I would guess that a lot of the bonding tips for two buns apply for your buns and ferrets, though you might not have as many territorial issues since they’re different species. Have some gloves on hand – like the decent work/gardening gloves, not rubber gloves, to protect your hands if you do have to break up a fight. Maybe a spray bottle of water to stop aggression. Oh and watch sharp claws and teeth to make sure no bunny/ferret gets hurt!
I don’t think they should ever be left alone together, even if they do get along when you’re in the room with them…
If anyone has experience with ferrets and bunnies, please correct me if I got anything wrong, since, like I said, I don’t have any experience with ferrets.