Z Burger, located in Tenleytown and Glover Park, is offering free burgers all day today on Thursday, April 2. Just mention the code word “yowza” to get a burger topped up the way you like. Cough up some dough for the Five Guys-like peanut oil fries or the yummy onion rings. But you may want to skip their custom shakes – the majority of which use the same flavored syrups you find at Starbucks. CORRECTION:…