Device lose root access after installing SU .zip update from stock recovery
SuperSU zip is an unsigned zip and can only be flagged through a custom recovery like cwm our twrp. You can search on xda for a custom recovery for your device. Use Kingroot to root your device again, use fastboot or ODIN from PC (refer to XDA  for proper device-specific instructions) or Flashify to flash a custom recovery image, then full unroot from Kinguser, and then flash the SuperSu zip from custom recovery.