The actual file I grabbed is RT-AC66U_3.0.0.4_264.22.zip
-rw-r--r-- 1 spent staff 24949853 24 Dec 08:40 RT-AC66U_3.0.0.4_264.22.zip
tried re-downloading it as well ... same error
OMG hold on .... maybe unzip the archive? close this thread before I embarrass myself more

... sorry I'm so used to flashing eveything from zip to img to specific dd to memory locations I assumed I just flashed the zip