As nouns the difference between metazoan and protozoan

is that metazoan is (zoology) any animal that undergoes development from an embryo stage with three tissue layers, namely the ectoderm, mesoderm, and endoderm the term applies to all animals except the sponges while protozoan is (cytology) any of the diverse group of eukaryotes, of the phylum protozoa, that are primarily unicellular, existing singly or aggregating into colonies, are usually nonphotosynthetic, and are often classified further into phyla according to their capacity for and means of motility, as by pseudopods, flagella, or cilia.

As adjectives the difference between metazoan and protozoan

is that metazoan is having to do with animals that develop from an embryo with three tissue layers while protozoan is of, pertaining to, or characteristic of a protozoan.