How effective to use zinc strip to prevent roof moss
Yes, it works - although most recommendations I've seen prefer zinc to copper (both more effective and cheaper).  In fact, you see it all the time on older roofs underneath galvanized roof fixtures.  For example, my neighbor's house:



Basically, each rain washes metalic zinc down the roof and basically prevents any growth and lasts for decades.  Copper does the same thing, although in that case it would be copper oxide washing down the roof.  Note that if the house is brick, you should go with the zinc - copper oxides react with periclase in bricks and can cause damage.

If you want some more reading, there's a short piece on the Oregon State website.