Welcome to HBT !!!
Did you dig the don't use grapefruit fact from a wine related source? I'd not heard that, interesting.
If your looking for a grapefruit flavor I believe there are some hops that can get you there, Centennials for one can be very grapefruit to me.
Personally I would not use zest of any fruit in an IPA but please come back here and post your trials if ya do.