I think it should work that way but I've never tried it, just be sure that the clean all option is selected if you opt for this way, since MiFlash automatically selects the lock option. I'm not sure how it works with Stable to Developer bootloader-wise, but if your bootloader is already unlocked then keep it that way, especially if the phone is not the China ROM version.
The way I did it the last time when MIUI 12 was in beta was flash the .zip with TWRP and then reboot to system. TWRP doesn't have an option to stop stock ROMs from replacing custom recoveries with stock ones so when you reboot it will switch to Mi Recovery. Once you boot into MIUI, if you already have internal test privileges just go into Updater and from the 3 dot menu select the option to download latest (full) package and reboot once it's complete. After that you'll be able to install OTAs normally.
Just to be sure (if you opt for the TWPR method) you could reboot to recovery before the Updater step, if it's Mi Recovery then you're good to go (to go back to OS just select the first option with the power button, it will probably be in Chinese).