Our recent Chandra and XMM-Newton observations of several high redshift quasars have revealed the presence of massive outflows of highly ionized, high-metallicity material driven from near the black hole (a few r_g) with velocities of up to 0.4c (Chartas et al. 2002, ApJ, 579, 169; Chartas et al. 2003, ApJ, 595, 85) The inferred mass outflow rates of the order of 10 M_solar/year and the measured outflow velocities, that significantly exceed the escape velocities of galaxies and clusters of galaxies, imply that quasar winds provide an important feedback mechanism for kinetic energy injection into the IGM. These quasar outflows may also play an important role in the coevolution of black holes and their host galaxies. The combination of the observed relativistic velocities and the estimated short recombination time-scales of the Fe XXV and/or Fe XXVI X-ray absorption lines imply that the X-ray absorber is launched closer to the black hole than the medium responsible for the UV absorption, thus may represent the shielding gas proposed in several theoretical studies of line-driven disk winds (e.g., Murray et. al. 1995, ApJ, 451, 498 ; Proga et al. 2000, ApJ, 543, 686). This suggestion is supported by our recent detection of significant variability of the properties of the X-ray absorption lines in APM 08279+5255 over a period of 1.8~weeks (proper-time). The extreme variability of the X-ray absorption lines combined with the lack of variability over time-scales of years in the velocity structures of UV broad absorption lines (e.g., Barlow 1993; Proga et al. 1995) implies that the X-ray and UV absorbers in quasars are likely distinct.