two ways
first is to delete the "0" values in the data series
second is to click on the graph line wait a short time and click on the
segnment you dont want and select just that segment.
select none for line.

there are other ways also

"rshalayda" wrote:

I want to create a line graph in Excel showing sales of three products. Two
of the products have 6 years of data, but the third has only been on the
market three years. How can I display only the last three years of data for
product 3 and eliminate the zeros that are assumed for years 1, 2 and 3? In
other words, I want to suppress the line segment that starts at zero in year
3 and rises steeply to the sales value in year 4 and show only the line
segments from years 4 to 5 and 5 to 6 for the third product.