he Block DM-SL includes a spherical LOX tank, a toroidal kerosene tank around the single 11D58M main engine, and a pressurized instrumentation compartment. These elements are connected with a truss structure. When integrated on the launch vehicle, the Block DM-SL is contained inside a cylindrical skin-stringer interstage that is jettisoned before Block DM-SL ignition. The interstage is divided into two sections, referred to as the lower adapter and middle adapter. The mass of these two components is 526 kg and 715 kg (1160 lbm and 1575 lbm), respectively. The stage can function for 24 h or more on orbit, and is capable of five to seven restarts, allowing complex orbital maneuvers. The Block DM-SL is capped by an aluminum interface skirt. This flared structure serves as the transition from the 3.7-m (12.2-ft) diam stage to the 4.15-m (13.6-ft) fairing, and also carries the conical payload support structure.

Other modifications from the "Proton" version include updated avionics, modified interfaces to the lower stages and the payload section, and modified prelaunch support interfaces. For example, on "Proton" the fueling and umbilical connections are provided by an umbilical tower. On "Zenit", these connections are routed up through the lower stages. The instrument compartment of the Block DM-SL is also mounted lower than in previous versions of the Block DM in order to provide clearance for the payload adapter. The four thrust chambers of the RD-171 engine can be individually gimbaled ±5 deg in one axis to provide three-axis control. One of the few differences between Zenit's RD-171 and the RD-170 used in the "Energia" strap-on booster is that the RD-170 engine supported two-axis gimbaling of each thrust chamber. Attitude control during second-stage flight is provided by the RD-8 vernier engine, which uses one turbopump to feed four thrust chambers, each of which can be gimbaled. The main engine is fixed and does not contribute to attitude control. The RD-8 burns the same LOX/kerosene propellant as the main engine and operates from 10 s before second-stage ignition to 75 s after main-engine shutdown. During third-stage burns, the main- engine gimbal provides pitch and yaw control, and turbopump bleed gas is used for roll control. The Block DM-SL upper stage also has two sets of independent ACS thruster units for three-axis attitude control during coast phases and payload deployment, and for propellant settling before main-engine ignition. These are fueled by small tanks of N₂O₄/UDMH.

The "Zenit 2" vehicle uses a digital flight control system. The navigation system is aligned using an optical update unit that is jettisoned on the pad immediately before launch. The "Biser-2" flight computer has three redundant channels, with majority voting to detect a failure in any channel. During Flight #31, two channels malfunctioned and were interpreted as failures by the remaining channel. As programmed, the remaining channel commanded flight termination rather than continue on a single channel, since there was no way to confirm that the remaining channel was not also faulty. Future vehicles will use the upgraded "Biser-3" computer, which has been modified to prevent this problem. As is typical with Soviet launch vehicles, flight termination is performed by automatic shutdown of the engines, which brings the vehicle down largely intact, rather than by triggering explosive systems to destroy the vehicle as is typically done in the West. However, the "Zenit 2" has a much more extensive flight safeguard system than most vehicles, probably stemming from early man-rating requirements for proposed spaceplane programs. The flight safeguard system can transmit a launch vehicle emergency signal to the spacecraft resulting from either an onboard computer failure or a loss of stability.