RSA PKCS#1 OAEP Padding Schema - padding 0 for first octet?
According to RFC 2437...

RSAES-OAEP can operate on messages of length up to $k-2-2\cdot hLen$ octets, where $hLen$ is the length of the hash function output for EME-OAEP and $k$ is the length in octets of the recipient's RSA modulus.
The padding string $\text{PS}$ in EME-PKCS1-v1_5 is at least eight octets long, which is a security condition for public-key operations that prevents an attacker from recovering data by trying all possible encryption blocks.


Generate an octet string PS consisting of $emLen-||M||-2\cdot hLen-1$ zero octets. The length of $\text{PS}$ may be $0$.


concisely,  the length of zero padding will be $${emLen-||M||-2\cdot hLen-1}$$

Running with OpenSSL;
openssl rsautl -decrypt -inkey priv2.txt -in cipher.txt  -raw -hexdump
and the first line of the output is;
0000 - 00 25 2b 2c e4 b5 a8 6c-a1 d1 cc bd 0b 26 d2 9c   .%+,...l.....&amp;..
You can see that the first byte above is 0x00