There are master programs in Zoology you can prefer to study like:

Master of Science in Marine Zoology
Master of Science in Zoology with specializations in Medical Microbiology
Master of Science in Zoology
Master of Philosophy in Zoology
Post Graduate Diploma in Life Science
Master of Business Administration
Post Graduate Diploma in Life Science

Some of the other specializations in this field are:
Arachnology
Entomology
Arthropodology
Apiology
Cetology
Anthrozoology
Conchology
Ethology
Helminthology
Mammalogy
Neuroethology
Myrmecology
Nematology
Ornithology

It shall depend upon your interest which one you want to pursue your higher studies in.

Good luck.