This is just a little bit long. Just about 10 minutes or so.
You don't need to worry about dying from the zombies. I couldn't figure out how to reload the weapons so it was just more trouble than it was worth. Just run by them and if you die, you will spawn nearby and can just continue forward. The only time you have to use a weapon is to explode the rocks.
Upon spawning, go forward and under a cave. Then, jump over a black water container to get to the main area. You will see some GREY rocks nearby the back of this area. One of the tents near this has an explosive weapon in it. Grab that and fire it at the grey rocks and it will blow them up. If you miss, just grab another explosive and but it into the barrel of the weapon.
Go through the new opened tunnel and there will be a ladder that you have to climb up. This is really glitchy to get up. Just grab onto it with a grip button (if you're on VR) and yank around a little bit. You will get up it eventually and will be able to see the exit. Same with this one, grab onto the platform with the grip buttons and just try to force yourself up. Jumping in real life may help too, to get you a little bit higher. I don't know if there's an easier way to do this, or if it's just glitched out.