面倒な手順の方が成功しそうじゃない?
What is ~そう ? Is is the contrary of ~そうにない ? So it would mean something like : "It's likely that you will succeed if you do it the hard way" ?
https://www.italki.com/question/353833
https://dictionary.goo.ne.jp/jn/129025/meaning/m0u/
"~そう" means "it seems", and "~そうにない" is the negative form.
More literally, your sentence would be "Doesn't it seem likely that you will succeed if you do it the hard way?", with "じゃない?" meaning "doesn't/isn't it?" here.