Can I claim home expenses with I am issued a T4 for employment income?

I am an over-the-phone interpreter and my employment requires me to work from home.  I was issued with a T4 for employment income but since I work from home, i want to claim part of my home expenses.   Should I claim my home expenses on T2125E Statement of Business or Professional Activities?  In my case, do I report $0 income on  T2125 form since I report it under Employment Income already?