While you need to employ both to get to a finished result, they cannot work in parallel no matter how much we might like to think so.
分析主干：they cannot work...
While 引导让步状语从句，尽管......。从句中的employ 表示采用，不定式to get...作目的状语。work in parallel并行不悖地起作用。no matter how 也引导让步状语从句，表示无论多么......。
译文尽管要完成定稿这两种思维都不可或缺，可是它们却不能并行着参与写作过程-----无论我们多么认为原本如此。