We present a possible design of future large-scale dark matter detector using liquid xenon. A low energy threshold is achieved by using a large CsI-coated internal photocathode for primary light collection. A focusing field, in the active volume and an electron focusing structure at the liquid surface, are used to transport free-electrons to the luminescence field. A 3D reconstruction of the events can be achieved by timing and location of the luminescent signal. A liquid xenon Compton veto and self-shield are integrated in the compact design. This detector could be used to probe most of the SUSY predicted dark matter. ZEPLIN IV can be initially tested at Boulby and then be moved to the USA to operate at a US deep underground science and engineering laboratory.