  Several early transition metal dipnictides have been found to host
topological semimetal states and exhibit large magnetoresistance. In this
study, we use angle-resolved photoemission spectroscopy (ARPES) and
magneto-transport to study the electronic properties of a new transition metal
dipnictide ZrP$_2$. We find that ZrP$_2$ exhibits an extremely large and
unsaturated magnetoresistance of up to 40,000 % at 2 K, which originates from
an almost perfect electron-hole compensation. Our band structure calculations
further show that ZrP$_2$ hosts a topological nodal loop in proximity to the
Fermi level. Based on the ARPES measurements, we confirm the results of our
calculations and determine the surface band structure. Our study establishes
ZrP$_2$ as a new platform to investigate near-perfect electron-hole
compensation and its interplay with topological band structures.
