I think that eggs are totally difficult to paint. Not the shape, but the texture and the color transitions, not to forget the incidence of light.
My goal was to make a small documentation in my nature sketchbook of the different eggs of our native birds in a size comparison.
Why are objects such as eggs so difficult to paint?
You have to let each layer of paint dry completly so that you can apply the next one. This is extremely time consuming and a good job for rainy days, where you can then pass the time with other things while waiting for the drying.
I found a very nice postcard, which showed very well the different sizes of the eggs. (link +here+).