Residency in a country is mutually exclusive. The second you establish residency outside of the US, your LPR status is forfeit. When you received and used your FLR, you forfeit LPR status. USCIS will see that when you send in a copy of your passport in your citizenship application, if you choose to do so.
From the USCIS website (emphasis mine(:
You may be found to have abandoned your permanent resident status if you:
Move to another country intending to live there permanently
Remain outside of the United States for more than 1 year without obtaining a reentry permit or returning resident visa. However, in determining whether your status has been abandoned, any length of absence from the United States may be considered, even if less than 1 year
Remain outside of the United States for more than 2 years after issuance of a reentry permit without obtaining a returning resident visa. However, in determining whether your status has been abandoned any length of absence from the United States may be considered, even if less than 1 year
Fail to file income tax returns while living outside of the United States for any period
Declare yourself a “nonimmigrant” on your tax returns