I have an Excel file with formulas in this manner:
=IF(OR(ISERROR(G16),ISERROR(G17)),X16,IF(OR(G16=\"xxx\",G16=\"yyy\",G16=\"zzz\"),Y16,IF(G16=\"333\",\"N\\A\",IF(
If you have a formula that looks like that, then to get a meaningful response you will have to post a sample workbook on a forum with clear instructions on what you are trying to achieve.
Yes, some of the answers above point out how you can view the formula better, or get rid of some superfluous stuff, or hide the complexity within some VBA (which in my opinion only addresses cosmetics, probably with significant expense in terms of greatly increased recalculation time).
But without knowing the intent of the formula - and of the workbook in which it sits - one can only offer so much advice.
If you have tens of thousands of formulas like this in your workbook, then you have a data structure problem, and not a formula problem. The most efficient formula is the one that is avoided. If you were to redesign this workbook from scratch so that it leveraged off of Excel Tables, PivotTables, and perhaps the Advanced Filter, then you would avoid tens of thousands of formulas like this one. Maybe hundreds of thousands of formulas.