100.3 Stereo Uno (Mazatlán)

Siempre 100.3 HD4 (XHZS-FM) is a radio station in Mazatlán, Sinaloa, broadcasting on 100.3 FM from a transmitter on Cerro El Caracol. It is owned and operated by Luz Network, which programs its Stereo Uno pop format.

XHZS received its concession on August 25, 1987. The station has had various formats over the years: it used the Estereo Vida brand until the mid-2000s, when it flipped to the Planeta pop format. In early 2012 it became the Los 40 Principales franchise, and in 2015 it adopted the @FM pop brand.

In May 2016, XHZS moved from Radiorama to MegaRadio affiliation and changed its name to Switch, as the previous brand was Radiorama-specific; the change was reversed in June 2017. On March 30, 2020, Luz Network took over ownership and operation of the station and began its Stereo Uno pop format, giving the company a presence in all three major Sinaloa cities, as it already owned stations in Los Mochis and Navolato–Culiacán. In 2022, the Federal Telecommunications Institute approved XHZS-FM to begin broadcasting in HD Radio.