for the roms and tools for Star Z2 can be found on "talkmobi" page you have to google search for it as i am unable to post links yet:
there are two sections you have to look at:
"rom download & flash guide" (top menu link + click on it) --- flash tools, drivers & tutorial get printer handy
and the second "fast card tech rom released july" (hover on the link above and a menu will apear after downloading the mtk tools and drivers from the link itself) --- on this list there is the official Star Z2 Rom do not forget to write down the 4 digit password you will need that code to unzip/unrar file as archives are password protected.
used them to unbrick my jiayu G3T now working flawlessly