Can any one provide a snippet to compare different timezones

As Lucian & richie have said it is rather unclear what you are actually are after. I'm assuming that you want to assert that two date/time strings in different time zones are the same time, if so here his some Groovy script to give you a starter for 10 as we don't know what your exact scenario is:

import java.text.SimpleDateFormat

// Parse date time strings to Groovy date objects
def dateTime1 = Date.parse('dd/MM/yyyy HH:mm:ss z','29/05/2018 17:00:00 GMT')
def dateTime2 = Date.parse('dd/MM/yyyy HH:mm:ss z','29/05/2018 12:00:00 EST')

// Just for debug/demo purposes output date times in the UTC time standard
def sdf = new SimpleDateFormat('dd-MMM-yyyy HH:mm:ss z')
sdf.setTimeZone(TimeZone.getTimeZone('UTC'))
log.info('Date/Time 1 = ' + sdf.format(dateTime1))
log.info('Date/Time 2 = ' + sdf.format(dateTime2))

// Assert date/times are the same
assert dateTime1 == dateTime2