The Pi Zero 2 has four cores, but runs at a stock 1 GHz, while the 3B+ runs at 1.4 GHz and the 4B at 1.5 GHz. More computing, more power. Test number two is sbc-bench which includes a memory ...
Otherwise, the new Zero 2 isn’t much different from the original ... they didn’t switch over to USB-C (at least for the power port) and micro HDMI to bring it in line with the Pi 4, but ...