In the current release(v1.6.2), you can do this using the "{EXP:}" token, using the "Text" tab:
Start Loop While : [{EXP:{SMALL:value1} = 0 AND {SMALL:value2} = 0 AND {SMALL:value3} = 0}] Equals '1'
Substitute the appropriate variable type token instead of "{SMALL:}" where applicable.
In the current beta(v1.6.4.1), you also have the option of using the new and convenient "Condition Builder" feature:
Start Loop While : ([value1] Equals 0 AND [value2] Equals 0 AND [value3] Equals 0)