We are concerned with a system of equations governing the evolution of isothermal, viscous and capillary compressible fluids, which is used as the phase transition model. In the case of zero sound speed, it is found that the linearized system admits a purely parabolic structure. Consequently, one can establish the global-in-time existence and Gevrey analyticity of Lp solutions in hybrid Besov spaces, which improves the prior L2 bounds on the low frequencies of density and velocity due to acoustic waves. The proof mainly relies on new Besov (-Gevrey) estimates for product and composition of functions.