Help with basic GE z-wave switch wiring

Here is a 3-way FAQ. Sounds like you may have your current wiring like the last diagram. That setup is not compatible with GE switches. You may want to look at Cooper or Linear that have add-on switches without needing travelers. Micro relays are also an option if that is the case. Feel free to share pictures as I may be interpreting what you said differently than what you actually have.