From the sound of it, they are using a digital delay pedal for the echo and a flanger or phaser pedal to get the eerie sound Standard Tuning EADGBE 2x e|--------------| b|--------6-----| g|--7-----------| d|-----0-----0--| a|--------------| e|--------------| 2x e|--------------| b|--------5-----| g|--6-----------| d|-----0-----0--| a|--------------| e|--------------| 2x e|--------------| b|--------3-----| g|--3-----------| d|-----0-----0--| a|--------------| e|--------------| 2x e|--------------| b|--------3-----| g|--2-----------| d|-----0-----0--| a|--------------| e|--------------|
https://primanota.net/misc-computer-games/glu-contract-killer-zombie-chords.htm