When creating a DHL Express shipment, if you can not validate an address, we recommend you to use the DHL Capability Tool.
This can help you to modify an address when getting this error from DHL:
Cannot determine destination service. Check recipient information and resubmit. If this problem reoccurs contact your customer service representative.
The DHL Capability Tool will show you which address fields are mandatory depending on country origin and destination.
Example below: you can see that Zip Code for Ireland isn't mandatory, but destination suburb is.
See also our post about DHL Zip Code format.