We plan to study by means of zero and longitudinal field muSR the static and dynamic magnetic properties of SrZnVO(PO4)2, a prototype of the S=1/2 J1-J2 model on a square lattice with competing ferromagnetic and antiferromagnetic interactions. This proposal is a continuation of our study of this class of materials. So far we have studied two compounds characterized by different frustration ratios J2/J1 which show quite a different behaviour of the mu+ relaxation rate, namely different spin correlations. Since SrZnVO(PO4)2 has a frustration ratio in between the one of those two compounds, it should allow to investigate how the spin dynamics evolve upon decreasing |J2/J1| towards 0.7, where long range magnetic order is expected to disappear and a bond-nematic order arise.