OpenSSL: best way to sha256 hash two sha256 hashes

Question

I have two sha256 hashes as hex strings

HASH1=b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c
HASH2=7d865e959b2466918c9863afca942d0fb89d7c9ac0c99