That looks like a winbond flash chip. I believe when I flashed my Asus VG248QE with the Mstar ISP device, the Mstar ISP also identified the Asus with that same flash chip. That's really strange.
I wonder what the RT809F and Mstar ISP device (I own them both) would identify your XL2720Z as. They both identify mine as MX25L1606E.