hi,

see I understand you are in great dilemma , however you have already studies bachelors, complete b.ed and masters course. now see the government  examinations vacancy differs every year and there is hard to predict for each year how many vacancy and streams would allow.

now coming to b.sc zoology, syllabus includes

• Ecology.
• Microbiology.
• Biochemistry and Cellular basis of life.
• Evolution and Genetics.
• Cell and Molecular Biology.
• Wildlife Forensics.
• Microbial Diversity.
• Biosphere.

so there is chemistry course includes in zoology syllabus but botany may not available as per course structure of most of the university. now if the additional course available in the college you may take botany as additional while studying b.sc zoology.

hope it would help.