Seem’s easy enough. Instructions are clear as day.There are a custom framework to be able to do firmware downgrade combine with MODORU from 3.71-3.72, but please dont try it if you dont have experience, because in normal case you only get softbrick and can install update from QCMA to get back into 3.71-3.72, but mess thing up with this is a complete hardbrick and your vita become a paperweight.
Here's the guide to do so, please read it all before trying:
https://www.psx-place.com/threads/m...71-3-72-by-thefl0w-skgleba.25972/#post-202127