istikhaara and zaicha

AS-salaam-o-ALaikum!! i wank to know that what is the difference between istikhaara amd zaicha?for example if we made istikhaara and the answer is that the person is better for you! but on another hand if we done zaicha then the answer is come that your stars are not meet with each other?what will be do then? please breif me!
i am very oblige to you!