[Advice requested] Merging subscribed .ical calendar into main calendar

[Vygotsky]

Hi, sincere apologies if I break any community rules, I'm a newbie here.

I work for a school organization with about 130 employees. We use Office365 for all of our internal communications. Now the issue is that, being teachers, we also rely on a third party tool producing our lesson schedules. This creates a problem when employees want to schedule an assignment with a colleague. Because although it is possible to import the lesson schedule into Outlook via an .ical url, the lesson schedule (obviously) doesn't show up for me when I look into the agenda of a fellow colleague. Therefore I can't really see whether he/she is available or not.

So my question is: would it be possible to import the .ical url in such a manner that it would actually merge with my main calendar so that colleagues can not only see my own appointments, but also my lesson schedule?

Any help is greatly appreciated!

[#2]

What third party application are you using for the scheduling?

They may have an APP which integrates with Outlook.

@Vygotsky 

[#3]

We use the third party application called "Zermelo". Its a relatively small Dutch company mainly serving schools.

They do have a separate android/ios app, and the aforementioned .ical subscription option, but that's not enough: colleagues can't see the calendars I'm subscribed to.

@Paras Dodhia