Need some input on cap gain taxes calculations

[Kimi Ho]

Hi All,
need to verify some calculations from my accountant. Need only rough calculations/numbers as I understand that the numbers depend on my income. 
bought a house in 2010 for 136k and sold 2020 for 340k (cap gain after fees about $170k). 
We did a 1031 exchange and bought another property in 2020 for 750k. We just have recently received an offer close to our asking price of 1.4 mil. 
I’d like to know what my taxes are roughly on both cap gains. 
may accountant said it would be around 420k for federal and 120k for state which would basically erase almost all gain. 
she used the base as 200k and the cap gain as 1.2mil which clearly is not the case. 
my calculations show 170k gain from first property and $475 from 2nd hence I should be paying cap gain taxes on 645k. 
if my accountant was right, it wouldn’t make sense to sell at all. 
any input I’d appreciated. Let me know if I’m missing any relevant information. Thanks