Tax liability on sale of 1st property after purchase of 2nd

Hello,
I plan to sell my Flat and invest the returns, adding some additional funds in another property to enjoy the ZERO tax benefits on LTCG.

However I found a new property which I want to buy and my 1st Flat is still for SALE.

If I use my other sources of Income added with Bank Loan and buy the 2nd property now... when I sell my 1st Flat 3 months later (perhaps during the same financial year), can the returns from this SALE can be considered as invested in my 2nd property which I bought 2 or 3 months before and enjoy ZERO tax or am I liable for LTCG on the SALE amount and pay tax or invest in Govt Bonds?

I highly appreciate any guidance from experts in this forum.

Thanks,
Gopi