Hi,
I'd use a Groovy step after Request 1 to check the value of interest, if it's there, I'd let the Request 2 step run. If it's not there, I'd 'jump' over request 2 to another step.
The below is some pseudo code to illustrate the Groovy Step to check the value from Request 1.
def requestOneValue = context.expand( '${StepName#Response}' );
if (requestOneValue == "0") {
// Do nothing here and let the test continue onto Request 2
} else {
// We don't have the value, so don't run Request 2.
log.info("Skipping Request 2");
testRunner.gotoStepByName("Name of first step AFTER request 2");
}