Although　relaxor　ferroelectrics　(RFEs)　have　received　considerable　attention　in　advanced　pulsed　power　capacitor　systems　(APPCSs)　due　to　their　numerous　advantages,　it　remains　difficult　to　achieve　comprehensive　outstanding　energy　storage　performance　(ESP)　owing　to　the　trade-offs　among　recoverable　energy　density　(Wrec),　energy　efficiency　(η)　and　thermal　stability.　In　this　work,　we　proposed　a　collaborative　optimization　strategy　for　improving　the　ESP　of　(Ba0.8Sr0.2)TiO3　(BST)-based　RFE　ceramics,　i.e.,　the　introduction　of　Bi(Mg0.5Zr0.5)O3　(BMZ)　and　the　use　of　viscous　polymer　process　(VPP).　The　former　obstructs　the　long-range　ferroelectric　order,　induces　high　dynamic　polar　nanoregions　and　broadens　temperature　stabilized　platform,　thus　alleviating　the　polarization　hysteresis　and　increasing　the　energy　efficiency.　The　latter　progressively　dilute　pore　concentration　and　thins　the　sample　to　∼70　μm,　which　can　greatly　improve　breakdown　strength.　As　a　result,　exceptional　ESP　parameters　are　simultaneously　achieved　in　0.85BST-0.15BMZ　ceramics　by　VPP　(BMZ15VPP),　which　exhibit　ultrahigh　Wrec　(10.3　J/cm3)　and　high　η　(88%)　under　720　kV/cm　while　maintaining　stable　temperature　stability.　It　is　also　noteworthy　that　a　superior　current　density　of　800　A/cm2　and　a　power　density　of　140　MW/cm3　are　obtained.　The　overall　excellent　performance　implies　the　competitiveness　of　BMZ15VPP　in　APPCSs　and　the　feasibility　of　this　strategy　in　designing　compositive　high　ESP　ceramic　systems.　©　2022　Elsevier　B.V.