Rumensin trade name for monensin is an ionophore antibiotic. It will kill protozoans like coccidia including the protozoa in the rumen. It will also kill gram positive bacteria, including those in the rumen. It is used not only as an anti-coccidial but to reduce problems in the rumen from feeding high concentrate diets because it kills the type of bacteria that produce lactic acid. It is considered to enhance growth, but mainly it helps put fat on the ruminant since more propionate is produced from the concentrates while reducing the problem of rumen acidosis. It works by inhibiting the movement of ions across the membrane of bacteria or protozoa.
Acts on the sporozoite stage so it can't continue to develop in the intestinal cell. Disrupts electron transport system in the mitochondria. Acts on the early stages of the life cycle
Amprolium (brand name Corid) is a vitamin B1 (thiamine) analog. The structure of the amprolium molecule is very similar to thiamine. The coccidia need thiamine to grow especially in stages where they are in high levels of reproduction. If they take in the amprolium instead of thiamine (amprolium competes with thiamine) then the cells cannot grow.
Sulfadimethoxine, brand name Albon.
Sulfa drugs block essential biomolecular pathways in the cells of protozoans and bacteria. Kills the coccidia in most of the stages by interfering with molecular pathways.
That's kind of brief, but I didn't have much time to put this together today.