Using Zillow for cash offer; or selling rental on Zillow

[Ray Valles]

I have a SFD Rental in N.C. and have noticed significant price increases on zestimate. I submitted to Zillow to provide me  "Cash Offer" on this property. They will get back to me soon. Has anyone used this "Cash Offer" with Zillow? Will they generally offer the zestimate amount or undercut? 

Also, I can place my rental for sale on zillow website; anyone have thoughts on this, or should I hire an agent to sell the property, just thought cost might be lower selling on Zillow.