How to process large updates with API?

I'm looking to sync local data with Zoho. This would be done in Accounts and in Contacts.

We will have more than 200 Accounts and more than 200 Contacts in Enterprise Edition.

How would I bulk fetch the Zoho data to perform a compare against local data? getRecords appears to only be able to get 200 records max... I don't even see how to get 200 at a time since 'from' and 'to' is specified rather than 'from' and 'limit'. Is the only way to get everything over 200 entries through an export? No export API so that wouldn't be so nice. I see this in the documentation:
For example, in Free Edition if you use the getRecords method, you can fetch a maximum of 200 records per request, in turn, a total of 50,000 records per day (250 x 200 = 50,000 records).
But I don't understand from the API docs how I'd actually fetch that many unique records.

After the data dump, we could identify new records and use insertRecords. There doesn't seem to be a documented limit on these, so good. Changed records, though, look like they'd have to be updated one call at a time through updateRecord and specifying the ID... and then I'm concerned about the API call limit. Is there a way to batch up the updates into a single API call?

Thanks a lot!