Their model was something like buy houses for 'market_price(house) * 95%' and then sell them for 'market_price(house)'. The article argues that they should have

Their model was something like buy houses for 'market_price(house) * 95%' and then sell them for 'market_price(house)'. The article argues that they should have devised a core complex model for asking prices, but an equally viable strategy would be to make sure their market price estimations were sufficiently accurate. That doesn't take any company specific information so it is entirely plausible (although false) that their Zestimate values would work well enough.