Public key aus PFX/P12:

openssl pkcs12 -in <zert>.pfx -nokeys -password pass:<passwort> -out <zert>.cert.pem   

Private key aus PFX/P12:

openssl pkcs12 -in <zert>.pfx -nocerts -nodes -password pass:<passwort> -out <zert>.key.pem

Private key in RSA Form:

openssl rsa -in <zert>.key.pem -out <zert>.rsakey.pem