What does ZH mean in the construction plan?

I found it online:

1 board b

2 roof board WB

3 hollow slab KB

4-slot circuit board CB

5-fold ZB

Six-rib MB

7 staircase slab TB

8 cover plate or ditch cover plate GB

9 Rainproof board or cornice board YB

10 crane safety walkway board DB

1 1 wallboard QB

12 TGB flume plate

13 beam l

14 WL roof beam

15 crane beam DL

16 monorail crane DDL

17 track connection DGL

18 parking CD

19 ring beam QL

20 lintel GL

2 1 connecting beam LL

22 foundation beam JL

23 staircase beam TL

24 frame beam KL

25 frame-supported beam KZL

26 roof frame beam WKL

27 purlin LT

28 roof truss WJ

29 bracket TJ

30 skylight CJ

3 1 frame KJ

32 rigid frame GJ

33 support ZJ

34 columns z

35 frame column KZ

36 constructional column GZ

37 bearing platform CT

38 equipment foundation SJ

39 piles ZH

40 retaining wall DQ

4 1 ditch DG

42-column supported DC

43 vertical support ZC

44 horizontal support SC

45 ladder t

YP canopy 46

47 balcony YT

48 beam pad LD

49 embedded parts m

50 skylight end wall TD

5 1 wire mesh w

52 steel skeleton g

53 basic j

54 hidden column AZ