The company also says the number of consumer-submitted reviews on the site has doubled in just over year with the rate of review submissions accelerating.
Zillow launched its review function, which provides the ability to post reviews on agents, mortgage and other real estate professionals in December 2010, but the content submission rate has significantly accelerated in the past 12 months.
The number of reviews has doubled since February 2015 and exceeded two million reviews near the end of March 2016.
"With huge acceleration in the rate of reviews submitted to Zillow, it's clear that reviews are becoming an indispensable part of the home buying and selling process," says Zillow Chief Marketing Officer Jeremy Wacksman.
"For buyers and sellers, knowing others' experiences with a particular agent or lender is incredibly useful as they search for a real estate professional.
"For agents and lenders, reviews have become a vital part of their marketing efforts. Every day we hear from real estate professionals who tell us how important reviews have been in growing their business."
Zillow uses a rigorous moderation process designed to ensure the reviews are high quality and credible. In order to post a review, every reviewer must have a Zillow account and must specify what service the agent provided.
Finally, all reviews are screened through proprietary Zillow fraud filters and read by a dedicated Zillow team.
Agent reviews are prominently featured as part of an agent's presence on Zillow, both when an agent appears next to a listing, as well as in Zillow's agent finder search tool.
Borrowers can find mortgage lender reviews in Zillow Mortgages, where they can also shop for mortgage rates and compare home loans side-by-side.