Zombies truly can't jump and while you are standing on the wooden boxes nothing can harm you. But mind that they can smash boxes and if they do, you are in a big trouble.
The apocalypse is real and zombies give no mercy to the livings. You won't give up even if they will surround you and your partner. Get armed and climb on the wooden box so they can't get you with their nails or teeth and shoot them before they figure out how to get you on the ground. Use special abilities when things will get nasty for both of you.