Separately, yes! Simultaneously, no! (Unless you try it through multi-component variable solubility solvent systems for the polymers and the solvents are specific for the chosen polymer and do not solubilize or cross over to the other solvent, means no intermingling of the polymer as solubilized products! This could be non-phase transfer situations, set of immiscible though may be tricky to create, if you could at all!). Just go and google about simultaneous Microspheres/NPs preparations! For microspheres, the try-out process suggested above would be easier to execute.