There must an algebraic formula, like, EURUSD divide with fix value 0.844 then divide it with USDCAD, Answer will always equal to ZARUSD etc.
No, there is no such formula. If you don't have any information about ZAR, then you cannot calculate ZAR/USD. It's as simple as that.
As an analogy, consider the following puzzle:
There are two brothers: an older brother and his younger brother. The two brothers don't have any other siblings. The older brother was born on the 7th day of the month. What day of the month was the younger brother born on?
The puzzle is obviously impossible to solve, because there are lots of families just like this one in the world, and among those families, different younger brothers were botn on different days of the month.
Therefore, if someone tells you that they can solve the puzzle, you know for a fact that they're certainly lying.
Likewise, there are lots of currencies just like ZAR in the world, and among those currencies, different ones have different values in relation to USD. Therefore, if someone tells you they have a formula for ZAR/USD without using any information about ZAR, you and I know for a fact that they're certainly lying.