ZenTime employs the hybrid optimization methodology of simultaneously optimizing a design at gate, transistor and physical levels of abstractions, to achieve large performance gains late in the design cycle. This technique combines key benefits of transistor-level optimization with the power of existing synthesis-oriented, highly automated design flows. From its inception, ZenTime has embraced open interfaces for its input/output, and works in a seamless manner with existing design tools and flows. The adoption of open interfaces has been instrumental in ensuring interface robustness, and in encouraging designer adoption of the hybrid optimization methodology. Results for several representative designs are presented, which clearly demonstrate the ability of designers to leverage ZenTime’s capabilities within their existing flows using standard open interfaces.