ppls

This sounds like a short term inequality b/w these two countries. in the long term when things return to parity these interest rates would be the same.

If you haven't read reading 19 yet I would suggest it. It goes into all the long term parity and short term inequality stuff.

Basically the linear approx. for the Internation Fisher Relation says it all:
in parity:

Int(FC) - Int(DC) = Infl.(FC) - Infl.(DC)

So, if inflation is zero in both countries, then the difference in interest rates b/w both countries (in parity) would be 0.

The IRP formula works only when assuming parity.