Find RegEx


Here I need a Regular Expression for find the words that start with a substring_of_length_3_containing_the_characters_as_i,o,nand_which_additionally_contains another_disjoint substring_containing_the_same_3_characters,
We can take an example as word "oniion",
cus here word start with characters i, o, n and_also_contain_the_ion(it doesn't matter whether it is uppercase or lowercae).
Can somebody pls come up with an idea??