Asus zenfone 6 E:failed to mount/ cache

Phone stucks on boot loading. wipe data/factory reset gives E:failed to mount/ cache error wipe cache partition also fails. abd sideload also give E:failed to mount/ cache Can't open vs.. Many same post suggest TWRP but i don't have it. Did not understand how to install it on a phone can't open. Many more says EMMC chip is dead. I hope it is not. I know it is very likely but i want to try other options first if i can.