This brief proposes a fully dynamic zoom ADC based on improved swing-enhanced floating-inverter amplifiers (SEFIAs) using the correlated-level-shifting (CLS) technique with $1250\times$ bandwidth/power scalability, by only changing the clock frequency. The improved SEFIA with CLS uses a reused capacitor to replace the dynamic biasing capacitor and input coupling capacitor, which simultaneously achieves both high gain and high output swing. Fabricated in a 55nm CMOS process, the prototype ADC with near-constant energy efficiency, which scales power from 453nW to $122~\mu \text{W}$ , achieves high resolution (> 95.2 dB) and high DR (> 96.7 dB) during the scalable bandwidth. At 5kHz BW, it achieves 97.3dB DR, 96.3dB SNDR, and 112.2dB SFDR, leading to FoMDR of 177.1dB and FoMSNDR of 176.1dB.