I am going to swap my brakes around (Shimano Zee and SLX) between two bikes but want to reuse the same hoses that are currently on each bike.

Do I need to fit new olives to each hose when doing this or can I reuse the existing ones?

Get new ones, for a quid or whatever it’s not worth the faff of trying to get them back in there and damaging the hose

If you can leave the olive on the hose and effectively swap the nuts then you can reuse them happily. You can get away with taking the olives off and reusing them if you need to but in this circumstance it’s better to fit new ones.

The only reason you’d need new olives is if you’re trimming the hose or you need different fittings. Otherwise it’s a pointless waste of time and money.

I don’t think you’ll get the olives off without cutting the hose so if you’re just swapping them over I’d leave them in place.
Edit too slow!

LOL – if you aren’t shortening the hoses then you’ll not want to be taking the olives off! They compress onto the hoses first time fitted.
Assuming the callipers and levers are identical in fittings then swap away, bleed and off you go.
Tim

[edit] what they said when I was typing :O)