All traditions of Buddhism emphasizes taking Refuge/initiation under a Guru/teacher.
The different “Vehicles” of Buddhist practice is due to the different levels of individuals capacity.
Hinayana: Also referred as “Small Vehicle“小乘…. those with limited capacity, practice to overcome attachment to this life and out of concern for their future well-being. Seeking for Self liberation alone.
Their practice focus on the basic five Buddhist precepts, and The Four Noble Truth. Which contained in the Buddha’s teaching referred as” first turning of wheel of Dharma”.
Mahayana: Also referred as “Great Vehicle“大乘 …. Seeking for Self liberation/Enlightenment,
for the benefit of all sentient beings. Practice the Bodhisattva Path. including Six Paramitas, complete understanding of Twelve links of cause and effects. Development of bodhichitta, that is great universal compassion toward all sentient beings Which contained in the Buddha’s teaching referred as “second turning of wheel of Dharma”.
Vajrayana: is a school of Mahayana, Also referred to as “Diamond Vehicle or Thunder boat” 金剛乘 . Practices including external Sutra teachings and internal practice of yoga meditation, which combined Mantra, Mudra, and visualization for speedy realization of Buddhahood in shortest time. Which contained in the Buddha’s teaching referred as “third turning of wheel of Dharma”.
Requiring initiation by the Guru / personal teacher on each stages of practice; the Preliminary Stage, Internal practice Stage, Secret tantric practice stage, and Completion stage. Mahayana teachings,. Seeking for Self liberation for the benefit of all sentient beings.
Tibetan Buddhism: four major schools of lineage traditions; they are schools of teachings Mahayana Buddhism, with advanced practice of tantric Vajrayana. The four schools are the Lyingma, the Kagyu, the Gelug, and the Sakya
Zen also is a school of Mahayana, transmitted from the Buddha to his disciple first patriarch Mahakashyapa, with unbroken lineage to twenty eighth patriarch Bodhidharma, a Buddhist monk whom traveled from India to China during the 5th century at old age of about 90 , he is the first
Besides teaching the Zen Buddhism, Bodhidharma also taught the physical training of the Shaolin monks that led to the creation of Shaolin Kung Fu. Zen’s teaching stanza verses “Not founded upon words and letters; By pointing directly to [one’s] mind.” 不立文字, 直指本心”
(Once again. Thank you to all who have contributed to this document taken from Wikipedia)