Traditional marine ecosystem models simulate the dynamics of nutrients, phytoplankton, zooplankton, and detritus. These so-called NPZD models have been developed into more sophisticated models with several functional forms coupled as a foodweb. The "Grand challenge" in marine ecosystem modelling is to achieve realistic end-to-end 3D models where the entire ecosystem is simulated from the physics all the way up through the foodweb. Models are now beginning to emerge that cover this range, with model systems such as ATLANTIS being parameterized for different ecosystems around the world. However, end-to-end ecosystem modelling poses a lot of challenges. Zooplankton play a crucial role in the ecosystems, and key challenges for end-to-end ecosystem models are representing the proper zooplankton diversity with regards to size, function, and parameterization of key processes. This is challenging for all types of marine ecosystem models and in particular for the end-to-end models that integrate different ecosystem components, including predators and prey of the zooplankton. The workshop will focus on presenting new ideas for improving the functionality of end-to-end models, emphasizing zooplankton implementation and how that affects the overall functioning and results of end-to-end ecosystem models.