Hi Mealea,
ZBrush was purchased by Maxon at the end of last year. We are now owned by the same company that develops Cinema 4D, Redshift and more.
Maxon is in the process of transferring all customer data from Pixologic to Maxon servers. So that is what some of the emails are about: First letting you know that the transfer will happen and then (after it has been completed) you will be given instructions for what you need to do.
Maxon is also running a brief promotion giving perpetual license users the option to switch to a yearly ZBrush subscription or a Maxon One subscription at a 50% discount. (The key word there was option - it’s not required.)
Here is an in-depth Q&A that was created: FAQ Regarding Maxon Emails to Legacy ZBrush Users - ZBrush (pixologic.com)