Here are just my own thoughts and opinions of what I would do.
Firstly, I would separate them completely. Out of sight/out of mind. Give them some time to “forget” each other before giving it another go. It might be impossible to bond them if you try again too soon. Give them a few weeks or even a month a part.
When you are ready to try again, I would set up two cages in a semi-neutral space, side by side. Wherever Zoe’s cage is–don’t put the two cages in that room, it will make Zoe territorial. Give them a few weeks side by side without any “dates” and see how they do. (Make sure there is a few inches between their cages so they can’t fight through the bars). This way they are doing daily things together; like eating pellets and greens, eating hay and pooping. Bring them out separately for exercise time in another room.
If this goes well–go back to stress bonding. Check out http://www.wheekwheekthump.com for some more info on different types of stress bonding. It looks like you’ve tried a few. What worked really well for us was a car ride (hubby drove and I sat in the back w/ the buns) followed by the bathtub. The bathtub is good b/c they have space to move, but not enough to circle and fight and it’s too slippery to chase.
This is just what I personally would do; but it might not work for you (I don’t know how much space you have to put two cages somewhere). Whatever you do–do not reintroduce them in a space that one bun has lived in or spend a lot of time in.
There are a lot of members on here who have done some really really hard bonds. Someone else might be able to chime in (my bond was pretty easy). Good luck!!!!