Hi Ead.. can you kindly confirm the model no.. is it DZ775SL-50K or DZ77SL ??
Well i checked it .. you wrote the model name wrong it was DZ77SL-50K.
For starters try flashing BIOS 0095 .. using method mentioned in below link
I confirm it's DZ77SL-50K. The BIOS could not be flashed but reconfiguring jumper settings to pin 2-3 allowed me to boot to BIOS and enable legacy boot.