Flexible zinc-ion batteries offer unparalleled adaptability for unconventional applications, reshaping the energy storage landscape. While both aqueous and non-aqueous chemistries within this family hold distinct advantages and limitations, understanding their intricate interplay is crucial. Aqueous systems prioritize safety and environmental friendliness through conductive gel electrolytes, while their non-aqueous counterparts chase superior energy densities with layered oxide cathodes exceeding 300 Wh/kg at the cell level. However, dendrite growth in zinc anodes and limited voltage windows in aqueous systems pose significant challenges. This chapter dives deep into these complexities, exploring strategies like surface modifications and electrolyte additives to tame dendrites and stabilize interfaces. The quest for higher energy density necessitates venturing into novel cathode materials and high-voltage compatible electrolytes, including ionic liquids. Beyond these technical hurdles, scaling up production and ensuring long-term cyclability remain key challenges for flexible zinc-ion batteries. This chapter equips students, engineers, and researchers alike with the technical insights and future directions to unlock the transformative potential of this technology, powering the future of wearable electronics, implantable medical devices, and beyond.