If you want to do medicine as career, why choose zoology. Other than MBBS, there are many courses like Bsc Nursing, BDS, BAMS, Bachelors in Medical Technology, Bsc in OT etc. Zoology as a whole has nothing to being in precise with human body and shall deal more with animal physiology and kingdoms. If you are a cropper, then I would suggest to study a year properly without joining any courses like Zoology etc.

If you have a Maths background, you might even choose Biotechnology.