Do I need a pump for my sprinkler zones that are minus 70 feet elevation?
From the position of the sprinklers you have 70 feet of head. You have shown that you have sufficient pressure.

What you need to consider is that if you have too many sprinklers then the pressure drops and so does the performance.

You will only need a pump if the area to be irrigated is too large and you need too many sprinklers....