Increase the Length of field - TaxZoneID

It’s doable, but I think you are asking for trouble. I once had to do it for another field and it turned into a nightmare. You will need to override every single DAC, alter every single tab where the TaxZoneID is referenced to change the length. With every new update you will need to review all these customizations.

Is there any other way to meet your business requirement *without* making this change?

I had a look and there’s 33 tables that will need to be updated, for your reference:

APInvoice ARInvoice BAccount BCBindingExt CAAdj CashAccountETDetail CROpportunityRevision CustomerClass EPEmployee EPExpenseClaim EPExpenseClaimDetails FSAppointment FSServiceOrder GLTranDoc Location Location PMProforma PMTaxTran POLandedCostDoc POLandedCostTax POLandedCostTaxTran POOrder POTax POTaxTran SOOrder SOTax SOTaxTran TaxReportLine TaxTran TaxZone TaxZoneDet TaxZoneZip VendorClass