int MessageBox (
    HWND hwndOwner,
    LPCTSTR lpszText,
    LPCTSTR lpszTitle,
    UINT fuStyle);
...
MessageBox (0, zMessageText, zWindowTitle, MB_OK || MB_SYSTEMMODAL || MB_ICONHAND);

push MBOK or MB_SYSTEMMODAL or MB_ICONHAND
push offset zWindowTitle
push offset zMessageTest
push 0
call MessageBoxA                ;call the library
add  esp,16                     ;remove arguments from stack