I had this use case come up when n8n.cloud was in early access - we wanted to invite people Mon-Thurs so that there was less chance of deployment related support tickets on the weekend. I used the Cron node and set the “mode” to custom. An input field is then available to enter a cron expression.
No expert in cron syntax but there are plenty of free sites that can generate cron expressions via a visual UI - would simply google “Cron expression generator”.
Regarding time zones, each workflow can override the instance’s default time zone. To do this, open a workflow then in left menu: Workflow> Settings> Timezone. Hope that helps!