In terms of zapier vs integromat I have used both before for various integrations, however not google calendar so won‘t be able to comment on this specifically. But have a look at the thread shared above as some users have shared their experience.
@Bastien_Siebman I tried the Asana premium 2-way sync with Google Calendar using zzBots. I like the easy setup, and the free plan is not too bad if you do not do a lot of synching.
However, if you delete or complete an Asana task, there is no corresponding action in Google Calendar. Also, when you add a Google Calendar event, it is synched over to Asana without an assignee. This is a problem if you use the Asana My Tasks since a task does not appear unless it is assigned to you.
Overall, I like ProjectBuddy better. It also has automatic 2-way synch that is almost instantaneous (vs. ten min. syncs for zzBots) and has delete/complete synchronization. I’m having problems getting the times to synch, but I’m working with ProjectBuddy to see if I’m doing something wrong. If I can get the times to synch, I will probably go with ProjectBuddy.
@Enric_Moreno See my reply to @Bastien_Siebman. ProjectBuddy looks promising, but I have to work through the problem of synchronizing times between Asana and Google Calendar.