Sync Contacts Across Sheets

I’m maintaining three separate Excel files that store customer data. None of them currently contain email addresses or phone numbers. I also have a master Google Sheet—kept in native Google Sheets format—that does include those missing contact fields.

Here’s what I need done:
• For every row in each Excel file, match against the Google Sheet on first name, last name, middle initial, and date of registration.
• When a match is found, pull across any email and/or phone number that exists in the Google Sheet and append it to the corresponding row in the same Excel file.
• The three Excel files must remain completely independent; do not merge them into one workbook.
• If the Google Sheet holds multiple identical matches, keep the existing row intact and simply enrich it with the extra contact details—no overwriting of other fields.
• All other data in the Excel files must stay exactly as-is.

Acceptable approaches include Power Query, VBA, Apps Script, or another repeatable method—whichever you prefer, so long as I receive:
1. The three updated Excel files with the new contact columns populated.
2. A brief note or script that allows me to rerun the sync in the future if needed.

Accuracy is vital; a quick cross-check report of records that could not be matched would be appreciated.