Hi,

It all depends on your interest and diligency that makes a subject difficult or easy to understand.

Theoretically speaking, Zoology is a bit easy to understand and relate to as compared to Botany, but practicals tend to be easier for botany.

Difficult and Easy are relative and subjective terms when it comes to studies. What makes a subject tough or easy is your interest / inclination towards that particular subject.

It's depends on you which subject you like most and can understand easily. You can not say which one is easy or not both are the branch of same that is biology.

Regards.