The　imperative　need　for　highly　active　bifunctional　electrocatalysts　accommodating　both　the　oxygen　evolution　reaction　(OER)　and　oxygen　reduction　reaction　(ORR)　has　intensified　for　the　development　of　advanced　rechargeable　Zn-air　batteries　(RAZBs).　Bifunctional　catalysts,　crucial　for　simplified　processes　and　enhanced　performances,　necessitate　additional　dimensions　to　host　a　greater　abundance　of　catalytic　sites　compared　to　their　monofunctional　counterparts.　Nanofiber　skeletons　with　multi-dimensional　nanostructure　building　blocks,　renowned　for　structural　tunability　and　high　porosity,　have　garnered　significant　interest　across　diverse　applications;　however,　their　synthesis　remains　a　formidable　challenge.　Herein,　we　present　an　innovative　synthesis　strategy　to　construct　nanofiber　electrocatalysts　with　three-dimensional　(3D)　hierarchical　building　blocks　(CoCNTs/PCNFs),　which　comprise　cobalt　nanoparticles　embedded　in　one-dimensional　carbon　nanotubes　growing　on　porous　carbon　nanofibers　that　expand　the　effective　number　of　OER　and　ORR　active　sites.　The　well-distributed　cobalt　nanoparticles,　coupled　with　the　large　specific　surface　area　and　high　conductivity　of　the　catalyst,　contribute　to　the　highly　desired　catalytic　properties　of　CoCNTs/PCNFs　toward　both　the　ORR　and　OER,　resulting　in　a　minimal　potential　gap　Delta　E　of　0.71　V.　Assembled　Zn-air　batteries　(RZABs)　incorporating　the　CoCNTs/PCNFs　catalyst　demonstrate　a　high-power　density　of　262.6　mW　cm-2,　surpassing　the　performance　of　state-of-the-art　Pt/C　and　RuO2　catalysts.　This　work　introduces　a　promising　strategy　for　designing　bifunctional　oxygen　electrocatalysts,　opening　avenues　for　future　advancements　in　the　field.　The　well-distributed　cobalt　nanoparticles,　coupled　with　the　large　specific　surface　area　and　high　conductivity　of　the　catalyst,　expand　the　effective　number　of　active　sites　to　achieve　high　catalytic　activity　toward　both　the　ORR　and　OER.