Impossible puzzle

[margotbean]

Looking at the cells highlighted in blue, what do I add to 27 to get zero, if not -27, which is already used?
Untitled.png

Edit: I see the error in my thinking, nvm, tyvm

[stubbornvulpes]

The two sides don't have to add to 0, just all 4 of the ones surrounding the middle, so 27, -37, and the two blanks are what adds to 0.