Introduction
In statistics, various measures are used to describe and analyze data sets. Some of the commonly used measures include the mode, median, mean, and harmonic mean. However, if any value in the data set is zero, it becomes impossible to compute the harmonic mean.

Explanation
The harmonic mean is a measure of central tendency that is used when dealing with rates or ratios. It is defined as the reciprocal of the arithmetic mean of the reciprocals of the individual values in the data set. Mathematically, the harmonic mean (H) is calculated as:

H = n / (∑(1/x))

where n is the number of values in the data set and x represents each individual value.

Reasoning
When any value in the data set is zero, it poses a problem in calculating the harmonic mean because division by zero is undefined. Since the harmonic mean involves taking the reciprocals of the individual values, the presence of a zero value would result in division by zero. As a result, the harmonic mean cannot be computed.

Example
Let's consider a simple example to illustrate this point. Suppose we have a data set with the values [2, 4, 0, 6, 8]. To calculate the harmonic mean, we would need to take the reciprocals of each value and sum them up. However, when we encounter the zero value, we cannot proceed with the calculation as division by zero is undefined. Hence, in this case, it is impossible to compute the harmonic mean.

Conclusion
In summary, if any value in the data set is zero, it becomes impossible to compute the harmonic mean. This is because the harmonic mean involves taking the reciprocals of the individual values, and division by zero is undefined. It is important to note that this limitation only applies to the harmonic mean, while other measures such as the mode, median, and mean can still be calculated even if zero values are present in the data set.