fun BigDecimal.convertCurrency(zecPrice: BigDecimal, isUsd: Boolean): BigDecimal
Convert this value from one currency to the other, based on given price and whether this value is USD. If starting with USD -> End with ZEC. If starting with ZEC -> End with USD.
isUSD - whether this value represents USD or not (ZEC)
Return
this BigDecimal value converted from one currency into the other, based on the given
price.