If you want to force a certain pronunciation, you can read more about that here using SSML tags. Currently, this is only possible with the English v1 model. We are working on adding this to the other models as well.
Alternatively, a workaround is to find an alternative spelling and write a word more phonetically. You can employ various tricks such as capital letters, dashes, apostrophes, or even single quotation marks around a single letter or letters.
As an example, a word like "trapezii" could be spelt "trapezIi" to put more emphasis on the "ii" of the word.