wont

to

years to become buddies.

are

Is there actual bloodshed? Injuries? If you haven't had many cats before, or
usually only have one, you may not be aware of the play that goes on. If
Fudge and Zoe are wrestling or chasing and there's nothing audible beyond
the pitter-patter of fuzzy feet, they may just be starting to play together.
Chasing for cats is just practice-hunting behavior, and often enough lions
swipe at the back legs of their prey to knock them down or trip them up, so
Zoe swiping at Fudge's legs may be play.

You should be able to call the SPCA from which you adopted Zoe and explain
the situation to them. But in my experience, unless you hear snarling or
screaming (which is more likely if it's outright aggressive attacks),
they're probably just playing.