你不能一心二用。

You can't do two things at once.

Source: Tatoeba

Sentence Composition

=1 你 nǐ you (informal, as opposed to courteous 您 nín)
=1 你 nǐ you (Note: In Taiwan, 妳 is used to address females, but in mainland China, it is not commonly used. Instead, 你 is used to address both males and females.)
2 不能 bùnéng
  1. cannot
  2. must not
  3. should not
=3 一心二用 yīxīnèryòng
  1. to do two things at once (idiom)
  2. to multitask
  3. to divide one's attention
=3 一心二用 yīxīn'èryòng to divide one's attention; to multitask