In ad hoc networks, ZRP (Zone Routing Protocol) combines a proactive routing protocol with an on-demand routing protocol. Proactive routing is adopted in the intra-zone, and on-demand routing is adopted in the inter-zone. During the process of the inter-zone routing maintenance in ZRP, there is a low reliability problem. So NHRP (New Hybrid Routing Protocol) was proposed, and the protocol reliability relationship between ZRP and NHRP was demonstrated by a comparative analysis on route reliabilities of ZRP and NHRP. The theoretical analysis shows that NHRP takes higher reliability than ZRP.