Surely, when you start getting to the realms of datasets with more than 65k rows, a spreadsheet is not the right repository. You need a database solution (Access maybe) or a flat-file solution.
Unless you're telling me that the recipient of a multi-sheet Excel file containing several-hundred-thousand rows is actually going to build multi-sheet analytics on it, or is an accountant (!), this requirement should be reviewed asap, in my opinion.
Go ahead - prove me wrong 🙂
If you haven't even tried to resolve your issue, please don't expect the hard-working volunteers here to waste their time providing links to answers which you could easily have found yourself.