存ぞん分ぶんに

Meanings

Used when someone does something without restraint, fully enjoying or indulging in an activity. Often used with verbs like 楽しむ, 語る, 泣く, etc.

思おもい切きりN3
思い切り and 存分に both mean 'to one's fullest', but 思い切り often carries a sense of bold, unrestrained force while 存分に is more neutral about simply doing enough.
思おもう存ぞん分ぶんN1
存分に is a shorter, slightly more formal way to say 'as much as one likes', while 思う存分 is the more common everyday phrase.
とことん
存分に means doing something as much as one likes or is satisfied with, while とことん implies pushing on to an absolute limit even against difficulty.
思おもいっきりN2
存分に is a more formal, polished way to say 'to one's heart's content', while 思いっきり is casual and more emphatic.
どしどしN1
存分に means doing something to one's heart's content without restriction, while どしどし specifically encourages someone to act boldly and without hesitation.

存分 (ぞんぶん) means 'as much as one thinks', from 存 (think) and 分 (portion). The adverbial form 存分に is used to mean 'to one's heart's content'.