"What I want to say it's to know what percent we have to find eggs over items from the explore feature"
At the time you wrote this, eggs had a 75% chance of being found vs a 25% chance of an item being found.
Eggs and items don't directly compete with each other. When your pet finds something it will either be an egg or an item. It's after that where egg and item rarity comes into play.
Your pet finds something. 75% it's an egg, 25% it's an item. Once item vs egg is chosen, then the individual chance is figured out with the specific item/egg rarities