Cashman,
I’d be skeptical about the zillow values too. Look at the comps. With the exception of one, the others are lower than your selling price. You would know better than we would about how comparable these other homes actually are. Without your former home actually selling, you don’t know what the true value is. Also, what about all of the extra monthly cash flow you have? How have you been investing that? When the time comes, you will have a nice nest egg to put down on the next property at a much lower price.
I’m with ibjames; take your profit, and don’t look back.