Convert from zettameter to hand [non-equine]

Unit Definition (zettameter)
The zettametre (or zettameter), symbol: Zm, is an SI metric unit of length. 1 zettametre is equal to 1e+21 metres, a very large distance. Not to be confused with a zeptometre.

Unit Definition (hand [non-equine])
The hand is a traditional unit of distance, now used mostly to measure the height of horses. One hand equals 4 inches, 1/3 foot, or 10.16 centimeters.