We introduce a novel design of a space-and-wavelength selective switch based on microring-assisted Mach-Zehnder interferometers. Multiple pairs of overcoupled microring resonators are incorporated as efficient and narrowband phase shifters and are driven in push-pull scheme. We design and demonstrate a 2×2×2λ elementary switch block with full spatial and spectral switching capabilities. The switching device's cross talk suppression and extinction ratio both exceed 21 dB. We measure over 75 GHz optical bandwidth per channel and less than 1.5 dB power penalty at 10-9 BER when two 32 Gbps on-off keying signals are loaded simultaneously. This new class of switching elements can further enable compact and high-performance space-and-wavelength selective switch fabrics without the need for wavelength (de)multiplexers or parallel switching planes.