Combine garlic, 1 tablespoon olive oil, jalapeño, zest and lime juice, salt, and peppercorns in a blender. Blend until garlic and jalapeño are finely chopped and black peppercorns have been broken up.
Pour marinade over shrimp and let marinate at least 15 minutes or up to 8 hours.
Heat remaining tablespoon of oil a large frying pan over medium-high heat. Once shimmering add shrimp with the marinade to the pan (careful, it will spatter). Cook, stirring occasionally, until shrimp is firm, pink and opaque, about 2-3 minutes.
Serve immediately with warm tortillas and condiments.