По совету Том Камминг
import { fromEvent, combineLatest } from 'rxjs'
import { filter, map } from 'rxjs/operators'
const upLeft$ = fromEvent(document, 'mouseup').pipe(filter((e) => e.which === 1), map(()=>Date.now()))
const upRight$ = fromEvent(document, 'mouseup').pipe(filter((e) => e.which === 3), map(()=>Date.now()))
const combined$ = combineLatest(upLeft$ , upRight$).pipe(filter((e)=> (e[1]-e[0])<=300 && (e[1]-e[0])>0), map((e)=> (e[1]-e[0])));
combined$.subscribe(() => {
console.log("It work!!!")
});