Convert from zeptometer to verst

Unit Definition (zeptometer)
The zeptometre (or zeptometer), symbol: zm, is an SI unit of metric length measurement. 1 zeptometre is 1e-21 metres, which is a very small distance

Unit Definition (verst)
An obsolete Russian unit of length. It is defined as being 500 sazhen long, which makes a verst equal to 3500 feet (1066.8 metres).