诸多 (zhū duō) is a formal adjective meaning 'many, a lot of', used almost exclusively for abstract things (factors, difficulties, aspects). It is more formal and literary than 许多 (xǔ duō) and 好多 (hǎo duō), and unlike 多 (duō) it cannot be used alone as a predicate or for concrete objects. 众多 (zhòng duō) is similar but often emphasizes a large crowd or multitude.