It is my understanding that we have to add "include:zohocrm.com include:zcsend.net" to our domain's SPF record in order for all Zoho services to work. Is this correct?

SPF records have a hard limit of 10 DNS lookups.  When we add zohocrm.com to our domain's SPF record, that causes 9 DNS queries alone!  For proof, look at this SPF tester site (it shows 8 lookups, which doesn't include the first one):   https://dmarcian.com/spf-survey/zohocrm.com

I strongly request that you reduce your SPF record down to only 1 query.  Your current one has several sub-queries because you are including **54** different IP addresses.  Do you REALLY expect to send email from 54 different IPs?  I would guess that you actually only need 1 or 2 IP blocks.  If you could reduce your SPF record down to only a few IP blocks, it would all fit in one record with no extra sub-queries.

Please let me know if I'm doing something wrong or if you'll fix this on your end.  We definitely need it to be fixed asap.