Zombies are able to stomp & destroy eggs through slabs, blocks, & even through a full block & a half of cover. Specifically I used a layer of prismarine brick blocks capped with another layer of dark pristine slab directly above some turtle eggs to shield them from attack. Zombies & baby zombies walked on top of the shelter, started jumping & destroyed the eggs as if they were in direct contact with them. I did not test with other materials yet.