I would suggest selecting the time zone that is associated with your physical location regardless of how many hours offset it shows from GMT. For example, we are in Florida, which is the Eastern Time Zone for the US. Generally there is a five-hour time difference between Eastern Time (EST/EDT) and time in the UK, which is currently on BST (British Summer Time GMT+1). GMT actually never changes, because it is considered to be a standard). At the end of BST it will then revert back to the same time as GMT. Be a aware that different locales start and end daylight savings on different dates.
Zoom Phone, I’m confident, will adapt to the correct hour when your timezone ends daylight savings.