Is version 2 of Zendesk module will block synchronisation if i did not subscribe ?
No.
Version 2 of module brings new features, including the ability of subscribe, but will not block synchronisation.
Nevertheless, after October 15th 2024, the Zendesk application will stop functioning for all companies that did not subscribe, whatever module version is used. Keeping an old version of the module to avoid subscription is useless.
Please refer
here for information about the transition to subscription-based model.