Since the discovery of the charmonium-like state X(3872) in 2003, a large number of new hadronic states have been observed in high-energy experiments (BESIII, LHCb, Belle, etc.), challenging the conventional quark-antiquark (meson) and three-quark (baryon) paradigms. Among various interpretations, hadronic molecules and diquark-antidiquark states have emerged as two important scenarios. Studies by different theory groups have shown that some of the observed tetraquark candidates can be well explained within both the molecular and the diquark-antidiquark frameworks. Therefore, we argue that in certain tetraquarks these two components should coexist with a certain proportion. Under this premise, we have recently proposed a new theoretical approach, namely, to consider the mixing effect between molecular and diquark-antidiquark states within an effective field theory framework. Specifically, based on the hidden local gauge symmetry, we introduce diquark fields and construct a complete set of interaction Lagrangians, including vertices for two light diquarks with one light meson, a heavy meson with a heavy diquark and a light diquark, and two heavy diquarks with one light meson.