What methodologies have proven most effective for integrating zero waste principles into urban sustainability frameworks while maintaining economic viability? In particular, what metrics and benchmarks can be adopted to quantitatively assess the efficacy of zero waste initiatives in metropolitan settings? Additionally, how might advances in recycling technologies and material recovery processes be leveraged to accelerate the adoption of circular economy practices, and what technical challenges are frequently encountered during the scaling of these initiatives? Discussion on approaches to harmonize policy, technology, and community engagement for sustainable waste management is welcome.