A lot vs. Alot: 9 Grammatical Pitfalls
1950, "to hit hard;" 1968, "to put into a stupor;" slang term, of echoic origin.
To omit from consciousness; shut out of the mind: I can just zone everything out and keep going (1960s+)
Intoxicated with narcotics; high
[1960s+ Narcotics; fr zone; influenced by spaced out]