Interesting comments, I can see 00's in the file
fully tested for .swf and don't atm think so...

No SWF / No ZIP

The script didn’t detect FWS/CWS/ZWS or PK\x03\x04 in the file.

No Valid zlib Streams

It searched for the common 0x78 DEFLATE signature at every offset and tried to decompress. All attempts failed.

binwalk Found Nothing

Binwalk typically reports recognized file signatures (like PNG, JPEG, zlib blocks, ELF binaries, etc.). It found no signatures.

7-Zip Also Fails

7-Zip tried to open it as an archive and reported Cannot open the file as archive.

But we certainly played with .swf game ... (Bitgo) and I can see the 00's