Hi,
I am 10x Salesforce certified application architect, having 9+ years of salesforce experience, I have done lot of third party integration and this wouldn't be really difficult for me.
I would recommend NOT to use Zapier, as with two disadvantages,
1. Data Security ( your data is your data and we need to take it seriously, Zapier has middle platform which can hold the data and it could be issues, if it's not falling into company data policy.)
2. API limits - Zapier uses the same API limits which you could use in your custom integration.
I would really recommend to use your own custom API integration, where you will have all the freedom to sync the data at your own way.
I hope this make sense.
Looking forward for great partnership ahead.
Thanks,