Another anecdote - We sold a house in late 2020, decided to get an offer through zillow first, since we had a newborn and staging would have been a hassle.

Zillow lowballed us 10% under their zestimate, and still tacked on an 8% fee - we ended up going with a realtor instead, and ended up getting 15% over the Zestimate, with a 6.5% fee.