Zero-and ultralow-field (ZULF) nuclear magnetic resonance (NMR) is a novel, portable, and cost-effective technique that enables high-precision chemical analysis through direct observation of intramolecular spin interactions at truly zero or very weak (weaker than 100 nT) external magnetic fields . Since in isotropic liquids direct magnetic dipolar interaction averages out to zero, in molecules with nuclei of spin smaller than one (absence of quadrupolar interaction), under the zero-field regime, an indirect spin-spin coupling (also known as Jcoupling) becomes dominant interaction . This allows to use zero-field NMR for the determination of a whole network of J-couplings in the molecule and hence enables identification and quantification of (bio-)chemical compounds . Furthermore, since exchange processes alter spin-spin couplings, this approach also enables monitoring chemical-exchange processes, involving, for example, chemical reactions (bond-breaking, bondmaking) or conformational modifications (bond rotation) . Thereby, ZULF NMR arises as an appealing spectroscopic modality for studies of chemical exchange of small biomolecules . This application was recently demonstrated in a context of molecules consisting of 2-5 coupled nuclear spins , but, for large spin systems, ZULF NMR spectra becomes complicated, due to increasing number of coupled nuclei, and its analysis is challenging. In this scope, herein, we present various ap-proaches of modifying and simplifying zero-field spectra of molecules, containing a large number of spins some of which can undergo a chemical exchange. For this purpose, we implement ZULF NMR J-spectroscopy to investigate aqueous solutions of urea, a molecule with a large spin coupling network and prominent proton exchange.