While Zillow is a good starting place to determine approximate value for your home when filing for bankruptcy, A better option would be a CMA -a comparable market analysis, or even better yet, a full blown appraisal.   When you are close whether your exemption covers the equity in your home, it's best to be certain as to value to avoid liquidation issues with a chapter 7 bankruptcy case.

http://www.abajournal.com/news/article/federal_judge_tosses_suit_claiming_zillow_zestimates_are_illegal_appraisals