Mix the olives with lemon zest and the olive oil in a bowl, stirring well. Cover and refrigerate while you prepare the rest of the ingredients.
Wash the potatoes well and place in a medium size pot. Cover by about 1 inch with cold salted water. Bring to a boil then reduce the heat and simmer gently until the potatoes are cooked through. Drain the potatoes in a colander and immediately add the coconut oil to them, stirring gently to coat. Season with the extra salt and freshly ground black pepper.
While the potatoes are boiling, with a knife carefully remove the corn kernels from the cob, and scrape the remaining juice as well. Add the kernels and the juice to a blender, along with the water, and blend until smooth. Strain the mixture through a sieve, using a flexible spatula to fully separate solids from liquid. Return the strained mixture to the blender. Halve the avocados lengthwise, remove the pits and scoop the flesh out and into the blender. Add the juice of the lemon, the torn soft part of the bread slice, and the scallion, rinsed and chopped. Process everything until creamy, then transfer to a serving bowl and stir in the crema, the sherry vinegar, the parsley and the salt.
Serve the trio right away, each component in an individual dish, and a fork for everyone. Dip an olive, dip a potato, rererepeat until gone.