Usually the iOS standard way works fine with Zendesk WeekCal as well. Please try that first. If you have problems, try the following method instead.
On the Koledarji page, select a calendar you like.
Click Izberi.
If you are not logged in to WebCal.Guru, you will not be able to modify subscription settings and you will have significantly smaller selection of calendars. In this case, jump directly to Step 4.
Adjust the subscription settings if needed and click Dodaj v Moje koledarje.
You will be taken to Moji koledarji page. On the calendar you just added, click next to Prenos and select Kopiraj naslov v odložišče.
On the home screen of the device, tap Settings.
Turn the device to portrait orientation, scroll down to Calendar and tap it.
Tap Accounts.
Tap Add Account.
Tap Other.
Tap Add Subscribed Calendar.
Tap the empty input field.
Tap Paste.
Tap Next.
Tap Save.
Updated 8 Feb 2023