Formula doesn't give same results when surrounded by brackets

I have a formula that is simply the following:

Formula:

=A1-SUM(B1,Z1)

The result of the formula = 0


However, if I then change that formula to surround it with brackets, so it is like this:

Formula:

=(A1-SUM(B1,Z1))

The answer ends up being 0.0000000000582076609134674

I get the same behaviour if that formula is nested in another formula, for example:

Formula:

=IF(Test, A1-SUM(B1,Z1), Value if False)

Why does adding brackets around the formula creating a (slightly) different result?