The 23-year-old has since joined up with his new Primeira Liga team Vitoria Guimaraes, after signing a pre-contract on a two-year deal in February this year.
Mosimane has previously expressed his sorrow at losing the a player who has been key over the last three seasons, while Zungu says the feeling is mutual.
"It's very, very sad [to be leaving Pitso]," says Zungu. "He wrote me a very emotional SMS, where he told me that he rates me amongst the best players he has ever coached – with the likes of Ricardo Katza, Daine Klate... That was very humbling.
"I will never delete that message. He's excited for me [to play abroad], perhaps with a bit of mixed emotions."
The Bafana Bafana midfielder also took the opportunity to praise his former mentor for his guidance and mentorship during his Chloorkop stay.
"He's a very humble guy and he's helped me a lot in life and career-wise," he adds. "He even helped me get back into the national team.
"He signed me as a young player, when I was scared to join Sundowns, but he told me, 'You know what, don't be scared man... This is football and you have to be mentally strong.'
"Being surrounded by such people helped me, even off the field regarding decisions I've had to make in my personal life."