He says that two days ago he found in his wallet shares from the Sheikh from 2009 that he had forgotten about, and he is asking about zakat on these shares.

If they reach the nisab, then zakat is obligatory on them.

As for the past years, we say he should look at those years.

He should review the profits and losses for each year, as that is easy, so look at the years that have passed.

Then for each year, he should see how much a full year has passed, evaluate that, then pay zakat from it, and look at these years, then deduct the amount of zakat that was paid from it.

The payment is from the first year, then he calculates it after deduction, then calculates it after deduction for the following year, then looks at how much remains after each year with the first zakat deducted.

Then he takes it out, and does the same in the second, third, fourth, and fifth year, until he reaches the year in which he has fulfilled his obligation. And Allah knows best. May Allah reward you with goodness.