Can Zoho required fields be removed?

I'm a brand new user and while trying to customize forms I ran across a problem. The example I will use is in "Contacts". I wanted to remove one of the required fields, in this case it was duration. And I also wanted to change the time fields from mandatory to non-mandatory. I found that I was limited in that regard. I could not change what was already mandatory nor could I remove the fields Zoho had deemed necessary. My question is why and if there is anyway to change this?

Thanks!