We present thermodynamic and neutron-scattering measurements on the quantum spin ice candidate Nd2Zr2O7. The parametrization of the anisotropic exchange Hamiltonian is refined based on high-energyresolution inelastic neutron-scattering data together with thermodynamic data using linear spin-wave theory and numerical linked-cluster expansion. Magnetic phase diagrams are calculated using classical Monte Carlo simulations with fields along [100], [110], and [111] crystallographic directions which agree qualitatively with the experiment. Large hysteresis and irreversibility for [111] is reproduced and the microscopic mechanism is revealed by mean-field calculations to be the existence of metastable states and domain inversion. Our results shed light on the explanations of the recently observed dynamical kagome ice in Nd2Zr2O7 in [111] fields.