For many people, especially those under 40, paying a friend, or settling a restaurant bill, or squaring up after happy hour isn't done in cash. It's done by peer to peer app.  You've probably heard of PayPal and Venmo, which PayPal owns. Now, there's some competition from Zelle, the big banks' answer to Venmo. Rahul Chadha follows peer to peer mobile banking for the research organization eMarketer.  His firm says Zelle will overtake Venmo this year. One thing that helps?  Zelle comes pre-installed in the mobile apps of many big banks. Chadha spoke with Marketplace's Lizzie O'Leary about whether that's enough to lift Zelle up. (07/30/2018)