There shouldn't be any reason to "disable" the NFZ functionality of your UAV. Although I don't specifically have knowledge of aviation rules in Brazil, I am picking the universality of aviation airspace would almost certainly mean Brazilian law relating to UAVs flying in a restricted airspace will be the same as other countries ranging from UK, US, Aus, NZ, Can, China. I could go on!
My ve
ry strong suggestion would be; if you have reason to fly within a NFZ area and can do so safely - meeting aviation requirements - then make an unlock request to Yuneec ahead of applying for appropriate authorisation from your Brazilian aviation authority.
Disabling the firmware/software though relatively easily achieved involves a process that is little short of hacking. Not a good move if you really don't know your way around software coding. Equally, and perhaps most importantly, governments the world over have been pushing very hard in the last few years to regulate UAV flying. Flying in a NFZ area, after disabling the NFZ firmware on your "bird" is potentially not only inviting you being prosecuted as well as confiscation of your UAV, it also plays right into the hands of media who seem to revel in the "bad news" stories about UAV's being flown in such situations. Lawmakers will also be more than happy to bow to public opinion around such media coverage, making it even harder still for all other UAV pilots to pursue their hobby, or business.
Follow the rule of law in your country. Don't risk putting other people in harm's way for the momentary gratification of thinking you've got one over Yuneec and the Brazilian aviation authority by disabling the NFZ function in your aircraft.
Enjoy the flying you are able to pursue legitimately

✌
