Trying to deflate a SAMLRequest in c++ with zlib. Result in Azure AD responding with not deflated propperly.

Question

I am trying to send a deflated b64 encoded url encoded string als a SAMLRequest trough a http. When i take my request xml and put it in an online deflator and b64 enc it comes out. I past it in the url and it accepts my request. However when i deflate the string with zlib in c++. I get a whole diffrent type of deflate b64 encoded string then most of the online encoders do.

Is there a different kind of deflation algorithm that azure ad sso uses as SAMLRequest then the deflate fuction of the zlib deflate.h uses? Or am i doing somthing wrong with the deflation in the first place.