Problem when generating certificate with zerossl

[reinforcers]

I have problem on my server, usually I generate certificate using Let's Encrypt provider. but, recently I want to try to use ZeroSSL. when I try to generate new certificate in one of my domain from control panel using the option "get automatic certificate from ACME provider", I already select zerossl as ACME provider but when it start to process the ACME use still Let's Encrypt. why is that?