REBCO bulk superconductors have broad application prospects in high-field magnets, magnetic levitation systems and other fields, but there is still a lack of effective sub-hundred-nanometer scale artificial pinning centers. Based on this, YGdBa₂Sr₂CuZrO_y nanoparticles were successfully fabricated via solid-state reaction sintering through half-site substitution of Gd with Y and Ba with Sr in the Gd₂Ba₄CuZrO_y matrix. To explore the influence of multi-element substitution on particle size and macroscopic properties of GdBCO bulks, we firstly prepared a series of single-domain GdBCO bulks via the RE+011 top-seeded infiltration growth (TSIG) method. The adopted solid-phase precursor was composed of (99-x) wt%(Gd₂O₃+1.2BaCuO₂) + x wt%YGdBa₂Sr₂CuZrO_y + 1 wt%CeO₂. The superconducting properties and microstructure of all samples were characterized by a 3D magnetic force and field testing system and scanning electron microscopy (SEM). The results indicate that: The size of Y and Sr co-substituted YGdBa₂Sr₂CuZrO_y nanoparticles have been reduced to a range between 120 nm and 40 nm. Compared with Gd₂Ba₄CuNbO_y nanoparticles with a minimum size of 100 nm, the grain size is reduced by 60%. The YGdBa₂Sr₂CuZrO_y nanoparticles are uniformly distributed on the GdBa₂Cu₃O_y substrate and act as effective magnetic flux pinning centers, significantly improving the physical properties of the single-domain GdBCO bulk samples. For the pristine sample, the maximum levitation force is 39.7 N, the maximum trapped field is 0.364 T (77 K, 0.5 T), and the field capture efficiency is 72.8%. At doping concentration x = 3, the sample reached its optimal properties in both levitation force and trapped field. Specifically, the peak levitation force hit 46.3 N, approximately 16.6% higher than the undoped counterpart. For the trapped field, the maximum value reached 0.443 T, marking a 21.7% enhancement over the undoped sample, with a capture efficiency of up to 88.6%. The study demonstrates that multi-element substitution increases the mixing entropy and chemical disorder of the system, thus refining the secondary-phase nanoparticles. These refined particles form dense flux pinning sites with enhanced pinning capability, which effectively improves the overall physical properties of REBCO bulk superconductors.