Minecraft wiki entry for Zombie, associated text: in a sufficiently shaded area: a sunlight level of 11 or less (a 1 block roof overhang provides sufficient protection even if it would have a sunlight level of 14);
in water;
wearing head armor (the helmet absorbs the damage from light but may take several day cycles to wear out completely).
under the status effect of Fire Resistance.
standing in cobwebs.[2]