Although computational fluid dynamics is well suited for modeling the dynamics of zero-net mass-flux (ZNMF) actuators, the computational costs associated with large-scale flow control simulations necessitate the use of simple models for these devices. A new model based on only the slot of ZNMF jets in grazing flows is proposed. A study of the dimensionless parameters governing the ZNMF jet in grazing flow is conducted, and the performance of the model is assessed in terms of the vortex dynamics and the mean integral quantities that define characteristics of the ZNMF jet. A comparison with full cavity simulations as well as the often-used sinusoidal, plug-flow model indicates that the new model provides a good prediction of the jet outflow. In addition, the fidelity of the model has also been explored for a canonical separated flow. Results show that the model is able to predict the effect of the jet on the separation bubble much more accurately than the conventional plug-flow model.