I will try to explain in on shorter word, e.g. word "že".

Writing in Apple's Notes:

1. write "ze" without accent above "z" character.
2. select "z" character
3. press "ˇ" accent - accent in highlighted rectangle replacing original letter is displayed
4. press "z" character - highlighted rectangle is replaced with letter "ž"
5. result is word "že"

1. write "ze" without accent above "z" character.
   

2. select "z" character
3. press "ˇ" accent - accent alone replacing original letter is displayed, the next letter in word is selected (highlighted) automatically
4. press "z" character - selected letter is replaced with letter "ž"
5. result is word "ˇž"